Double synthetic antiferromagnet using rare earth metals and transition metals

A mechanism relates to magnetic random access memory (MRAM). A free magnetic layer is provided and first fixed layers are disposed above the free magnetic layer. Second fixed layers are disposed below the free magnetic layer. The first fixed layers and the second fixed layers both comprise a rare earth element.

BACKGROUND

The present invention relates to magnetic random access memory (MRAM), and more specifically, to using rare earth and transition metals in reference and dipole layers.

A spin torque magnetic random access memory (MRAM) device uses a two terminal spin-torque based memory element. The two terminal spin-torque based memory element includes a pinned layer, a tunnel barrier layer, and a free layer in a magnetic tunnel junction (MTJ) stack. The pinned layer is also called the reference layer. The magnetization of the pinned layer is fixed in a direction such that when current passes through the MTJ stack the free layer becomes either parallel or anti-parallel to the pinned layer. Resistance of the device depends on the relative orientation of the free layer and the pinned layers.

SUMMARY

According to one embodiment, a magnetic random access memory (MRAM) device is provided. A free magnetic layer is provided, and first fixed layers are disposed above the free magnetic layer. Second fixed layers are disposed below the free magnetic layer. The first fixed layers and the second fixed layers both comprise a rare earth element.

According to one embodiment, a method of forming a magnetic random access memory (MRAM) device is provided. The method includes providing a free magnetic layer, disposing first fixed layers above the free magnetic layer, and disposing second fixed layers below the free magnetic layer. The first fixed layers and the second fixed layers both comprise a rare earth element.

According to one embodiment, a magnetic random access memory (MRAM) device is provided. The MRAM device includes a free magnetic layer, a first synthetic antiferromagnet (SAF) above the free magnetic layer, a tunnel barrier sandwiched between the free magnetic layer and the first synthetic antiferromagnet, a second synthetic antiferromagnet below the free magnetic layer. The first synthetic antiferromagnet and the second antiferromagnet both comprise a rare earth element. An oxide layer is sandwiched between the free magnetic layer and the second synthetic antiferromagnet.

DETAILED DESCRIPTION

Spin torque MRAM requires that the magnetic tunnel junction (MTJ) stack has a well-centered hysteresis loop with zero offset field. The dipole field emanating from the reference layers acts on the free layer and offsets the free layer hysteresis loop so that it is not centered on zero field. When the free layer hysteresis loop is not well centered the activation energy, required for data retention, is reduced. State-of-the-art techniques require using a synthetic antiferromagnet containing a 0.4 nanometer (nm) ruthenium (Ru) spacer, which is difficult to manufacture. If a dipole layer uses a rare-earth metal in the state of the art, there is no way to set the (magnetic moment) dipole layers in the correct direction reliably.

According to an embodiment, a spin torque MRAM device can use two (or more) rare-earth and transition metal multilayers. The two rare earth and transition metal multilayers include one layer as a reference layer (in which the reference layer contains a thin nonmagnetic spacer such as a tantalum (Ta) nonmagnetic spacer) and one layer as a dipole layer. Although tantalum may be utilized as one option, the nonmagnetic spacer layer does not need to be made from tantalum. The nonmagnetic spacer may also be made from niobium (Nb), tungsten (W), molybdenum (Mo), zirconium (Zr), and/or any other non-magnetic material. The thin Ta nonmagnetic spacer is not required to be continuous (i.e., the material may have holes in it) and thus is easily manufacturable. Although in one implementation, the Ta nonmagnetic spacer may be continuous if desired. The nonmagnetic spacer enables the coercivity, Hc, of the reference layer to be tuned to a low value. However, the dipole layer has a very large coercivity Hc. In this way, there is a large window between the Hc of the reference layer and Hc of the dipole layer, so that every bit can be set correctly.

In materials science, the coercivity (Hc), also called the coercive field or coercive force, is a measure of a ferromagnetic material to withstand an external magnetic field. The coercivity is the amount of magnetic field required to switch the magnetic moment of the reference layer and dipole layer, respectively.

Now turning to the figures,FIG. 1illustrates a magnetic random access memory (MRAM) device100. As shown inFIG. 1, MRAM device100includes a reference layer125(also referred to as a pinned magnetic layer), a tunnel barrier layer120, and a free magnetic layer115adjacent to the tunnel barrier layer120. The reference layer125, tunnel barrier layer120, and free magnetic layer115form a magnetic tunnel junction (MTJ) stack.

The MRAM device100also includes an oxide seed110adjacent to the free magnetic layer115and a dipole magnetic layer105adjacent to the free magnetic layer115. The oxide seed110helps to make the free magnetic layer115have perpendicular magnetization.

The reference magnetic layer125may be formed of iron platinum (FePt) or iron palladium (FePd). The reference magnetic layer125may be formed of at least one of platinum (Pt) or palladium (Pd), and at least one of cobalt iron CoFe or cobalt (Co). The tunnel barrier layer120may be formed of magnesium oxide (MgO). The oxide seed110may be formed of MgO. The dipole magnetic layer105may be almost identical to the reference magnetic layer125, in order to cancel out the stray field (exhibited upon the free magnetic layer115).

The magnetic moment of the reference magnetic layer125is shown by a downward pointing arrow. The magnetic moment of the dipole magnetic layer105is shown by an upward pointing arrow, which means the stray fields caused by the magnetic moments of the dipole layer105and reference layer125are intended to cancel out one another. The magnetic moment of the free magnetic layer115is shown by a double arrow indicating that the magnetic moment can be switched either up or down according to the direction of an applied current from the voltage source130. The magnetic moments of the reference, free, and dipole layers are all perpendicular to the plane of MRAM device100.

The free magnetic layer115has a magnetic moment that is either parallel or anti-parallel to the magnetic moment of the pinned reference magnetic layer125. The tunnel barrier layer120is thin enough that a current through it can be established by quantum mechanical tunneling of conduction electrons. The resistance of the free magnetic layer115changes in response to the relative orientation between the free magnetic layer115and the reference magnetic layer125. For example, when a current (i) passes down through the MTJ stack in a direction perpendicular to the MTJ stack layers, the magnetic moment of the free magnetic layer115is rotated parallel to the reference layer125(i.e., “1” memory state), resulting in a lower resistance. When a current (i) is passed up through the MTJ stack, the magnetic moment of the free magnetic layer115is rotated antiparallel to the reference layer125(i.e., “0” memory state), resulting in a higher resistance.

In the state of the art, there are not materials utilized that give large enough Hc (e.g., Hc>2000 oersted (Oe)), and that provide a large enough window between the Hc of the reference magnetic layer125and the Hc of the dipole layer105.

It might be desirable to have one Hc small such as approximately (˜) 3 kiloOe (kOe) and to have the other Hc large such as approximately (˜) 15 kOe according to an embodiment (shown inFIG. 2). This would provide a large window or large difference (15−3 kOe=12 kOe) between the required switching field coercivity (Hc) of the reference magnetic layer (250) as opposed to the dipole magnetic layer (260) according to an embodiment.

Assume that the Hc of the reference layer is higher than the Hc of the dipole layer. To set the magnetic moments of both the reference layer125and the dipole layer105, a large magnetic field at least equal to the larger Hc of the reference layer is applied downward on the MRAM device100to set the magnetic moments of both the reference layer125and the dipole layer105down. If the Hc of the reference layer125is 1 kOe and the Hc of the dipole layer105is 0.5 kOe, then the large magnetic field to set the magnetic moments is at least 1 kOe. As such, this large magnetic field (of, e.g., 1 kOe) switches both magnetic moments down.

To set the magnetic moment of the dipole layer105upward, a smaller magnetic field pointing up is applied. This smaller magnetic field is to be at least 0.5 kOe (but less than 1 kOe) to switch the magnetic moment of the dipole layer105(with Hc of 0.5 kOe) but not the reference layer125(requiring Hc of 1 kOe). However, in the state of the art, the Hc of the reference and dipole layers may not always be exactly the same for all junctions, and so there is not a large window between/separating the respective Hc of reference and dipole layers. When using the smaller magnetic field of 0.5 kOe to set the dipole magnetic layer105(having Hc=0.5 kOe), the magnetic moment of the reference layer125may inadvertently be set on some of the junctions in the memory array because of the small window between the Hc of the reference layer125and the dipole layer105. As understood by one skilled in the art, there are multiple MRAM devices connected in an array.

According to an embodiment,FIG. 2illustrates a magnetic random access memory (MRAM) device200. The MRAM device200has the tunnel barrier layer120, free magnetic layer115, and oxide seed110as discussed inFIG. 1. Additionally, MRAM device200includes reference magnetic layer_2220adjacent to a nonmagnetic spacer layer225, and a reference magnetic layer_1adjacent to both the nonmagnetic spacer225and the tunnel barrier layer120. On the other side of the free magnetic layer115, a dipole magnetic layer_1210is adjacent to the oxide seed layer110, and a dipole magnetic layer_2205is adjacent to the dipole layer_1210.

The reference layer_1215and the reference layer_2220have opposite pointing magnetic moments and together form a synthetic antiferromagnet (SAF). The combination (and combined effect) of reference layer_1215and the reference layer_2220, along with the nonmagnetic spacer225acts as a single reference magnetic layer250. The reference magnetic layer250has its own Hc, which is the combined effects of the Hc for reference magnetic layer_1215and reference magnetic layer_2220(as reduced by the nonmagnetic spacer225)

The dipole magnetic layer_1205and the dipole magnetic layer_2210have opposite magnetic moments and together form a synthetic antiferromagnet (SAF). The combination (and combined effect) of dipole magnetic layer_1205and the dipole magnetic layer_2210acts as a single dipole magnetic layer260. The dipole magnetic layer260has its own Hc, which is the combined effects of the Hc for the dipole magnetic layer_1210and dipole magnetic layer_2205.

InFIG. 2, the dipole magnetic layer_1210, dipole magnetic layer_2205, reference magnetic layer_1215, reference magnetic layer_2220are all made out of rare-earth metal and transition metal multilayers and/or rare-earth metal and transition-metal alloys. For example, the rare-earth metal and transition-metal alloy may be CoFeTb. In another example, the rare-earth metal and transition-metal multilayers may include one or more alternating layers of a layer of CoFe, a layer of Tb, a layer of CoFe, a layer of Tb, and so forth.

A rare earth element (REE) (or rare earth metal) is one of fourteen rare earth elements composed of the lanthanide series. The rare earth metals are found in group 3 of the periodic table, and the 6th period. Rare earth elements in the lanthanide series include cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Terbium (Tb) and gadolimium (Gd) work better than other rare earth elements, since Tb and Gd provide more perpendicular magnetic anisotropy.

The transition metals which are ferromagnetic at room temperature include iron, cobalt, and nickel.

Use of the nonmagnetic spacer225(e.g., 2 angstroms (Å) of Ta) in the reference magnetic layer250(which is utilized to increase magneto resistance (MR)) creates a low direct write field (Hd) for the reference magnetic layer250, such as Hc is approximately (˜) 3 kOe. Note that in a special case the direct write field Hd of reference magnetic layer250is equal to Hc, such that Hd=Hc=3 kOe for the reference magnetic layer250. The dipole magnetic layer260does not include the Ta nonmagnetic spacer, so the dipole magnetic layer260has a very large Hc (in comparison to the reference magnetic layer250), such as Hc˜15 kOe. This difference in Hc (between the dipole and reference layers) allows enough margin to set the directions for the magnetic moments for both the dipole magnetic layer260and reference magnetic layer250. To set the MRAM device200, first apply a positive field of more than 15 kOe to set the magnetization of both dipole layer1and reference layer1pointing up. Then apply a field between 3 and 15 kOe, for example 9 kOe, to reverse only the reference layer1(make it point down), while leaving the dipole layer1pointing up.

According to an embodiment, the Hc (e.g., 3 kOe) of the reference magnetic layer250maintains the same relationship as a function of temperature to the Hc (e.g., 15 kOe) of dipole magnetic layer260because the same materials are utilized in both the reference magnetic layer_1215and the dipole magnetic layer_1210and the same materials are utilized in both reference magnetic layer_2220and dipole magnetic layer_2205. Also, the Hc of the reference magnetic layer250and the Hc of dipole magnetic layer260have a large window of separation between the two, and the Hc of the reference magnetic layer250and the Hc of dipole magnetic layer260both change in the same manner with temperature.

The reference magnetic layer_1215, the reference magnetic layer_2220, the dipole magnetic layer_1210, and the dipole magnetic layer_2205each has its own magnetic moment pointing in a respective direction. Each individual magnetic moment (in the reference magnetic layer_1215, the reference magnetic layer_2220, the dipole magnetic layer_1210, and the dipole magnetic layer_2205) creates/generates a dipole field. Dipole fields, sometimes referred to as stray fields, can act upon the free magnetic layer115. The dipole fields (corresponding to respective magnetic moments) created by the reference magnetic layer_1215, the reference magnetic layer_2220, the dipole magnetic layer_1210, and the dipole magnetic layer_2205are configured to cancel each other out at the position of the free layer; this cancellation of the dipole fields (that affect the free magnetic layer115) is because of the construction of equal and opposite dipole fields in reference magnetic layer250and dipole magnetic layer260.

Cancellation of dipole fields happens between reference magnetic layer_2220and the dipole magnetic layer_2205. Particularly, the dipole field of the reference magnetic layer_2220is cancelled out by the dipole field of the dipole magnetic layer_2205. The reference magnetic layer_2220and the dipole magnetic layer_2205are made of the same material (such as, e.g., Co, Fe, and Tb in one case, or Co, Fe, and Gd in another case) and have the same thickness (in the z axis) but have magnetic moments in the opposite directions. Having magnetic moments in opposite directions allows for dipole fields in the opposite direction, thus cancelling the dipole field (or stray field) effect on the free magnetic layer115from reference magnetic layer_2220and the dipole magnetic layer_2205.

Similarly, cancellation of dipole fields happens between reference magnetic layer_1215and the dipole magnetic layer_1210. Particularly, the dipole field of the reference magnetic layer_1215is cancelled out by the dipole field of the dipole magnetic layer_1210. The reference magnetic layer_1215and the dipole magnetic layer_1210are made of the same material (such as, e.g., Co, Fe, and Tb in one case, or Co, Fe, and Gd in another case) and have the same thickness (in the z axis), but have magnetic moments in the opposite directions. Having magnetic moments in opposite directions allows for dipole fields in the opposite direction, thus cancelling the dipole field (or stray field) effect on the free magnetic layer115from reference magnetic layer_1215and the dipole magnetic layer_1210.

In a typical MRAM device, the operational temperature may change from between 0-85° Celsius (C.), which causes a change in the magnitude of the magnetic dipole field, along with a change in Hc. However, since the material and thickness are identical in both the reference magnetic layer_1215and the dipole magnetic layer_1210, the magnitudes of their respective dipole fields change in the same amount (i.e., change in the same values). For example, when the magnitude of the dipole field for reference magnetic layer_1215increases because of a change in temperature, the magnitude of the dipole field for the dipole magnetic layer_1210increases in the same amount. This also occurs when the magnitudes decrease because of a change in temperature.

Similarly, since the material and thickness are identical in both the reference magnetic layer_2220and the dipole magnetic layer_2205, the magnitudes of their respective magnetic dipole fields change in the same amount (i.e., change in the same values). For example, when the magnitude of the dipole field for reference magnetic layer_1215increases because of a change in temperature, the magnitude of the dipole field for the dipole magnetic layer_1210increases in the same amount. This also occurs when the magnitudes decrease because of a change in temperature.

Accordingly, the reference magnetic layer_1215and the dipole magnetic layer_1210have equal magnitudes and opposite dipole field directions, where their magnitudes have the same temperature dependence. Likewise, the reference magnetic layer_2220and the dipole magnetic layer_2205have equal magnitudes and opposite dipole field directions, where their magnitudes have the same temperature dependence. This means any temperature dependence of the reference magnetic layer_1215and the dipole magnetic layer_1210is automatically compensated for. Similarly, any temperature dependence of the reference magnetic layer_2220and the dipole magnetic layer_2205is automatically compensated for.

The reference magnetic layer_1215may have a thickness (in the z-axis) ranging from 1 nm to 10 nm and likewise the dipole magnetic layer_1210may have a thickness (in the z-axis) ranging from 1 nm to 10 nm. The reference magnetic layer_2220may have a thickness (in the z-axis) ranging from 1 nm to 10 nm, and similarly the dipole magnetic layer_2205may have a thickness (in the z-axis) ranging from 1 nm to 10 nm.

FIG. 3is a graph300illustrating the magnetic dipole field created by the double synthetic antiferromagnet (SAF) (reference magnetic layer_2220and reference magnetic layer_1form the first SAF while dipole magnetic layer_1210and dipole magnetic layer_2205form the second SAF) and exhibited (felt) on the free magnetic layer115in the MRAM device200according to an embodiment. The magnetic dipole field for the double SAF is plotted as waveform305. InFIG. 300, the y-axis shows the magnetic dipole field as Hz (Oe), which means that the magnetic dipole field was measured in the z direction inFIG. 2. Although the magnetic dipole field may flow in more than the z-axis direction (such as x-axis and y-axis), for purposes of the graph300(along with graph400), the graph300illustrates how the magnetic dipole field Hzacts upon the free magnetic layer115in the z-axis direction.

In the graph300, the x-axis illustrates the radial coordinate in the middle of the free magnetic layer115. In this example, assume that the diameter of the MRAM device200is about 30 nanometers (nm), and therefore the diameter of the free magnetic layer115is about 30 nm. Considered from a cross-sectional view point as shown inFIG. 2, the center of the free magnetic layer115is to have the radial coordinate 0. When starting from the center, moving to the right in the x-axis direction traverses from 0 nm to 15 nm, and moving to the left traverses from 0 nm to −15 nm (where −15 nm means traversing the opposite direction along the free magnetic layer115).

For the calculation in graph300inFIG. 3, the tunnel barrier layer120is made of MgO and has a thickness of 1 nm, the free magnetic layer115is made of CoFeB and has a thickness of 2 nm, the oxide seed layer110is made of MgO and as a thickness of 1 nm, the reference magnetic layer_2220is made of CoFeTb, has a thickness of 10 nm, and has a saturation magnetization Ms=800 emu/cm3(where emu is the electromagnetic unit), and the nonmagnetic spacer225is made of Ta and has a thickness of 0.2 nm.

Also, for the experiment in graph300inFIG. 3, the reference magnetic layer_1215is made of CoFe, has a thickness of 1.5 nm, and has a saturation magnetization of Ms=800 emu/cm3, the dipole magnetic layer_1210is made of CoFe, has a thickness of 1.5 nm, and has a magnetization of Ms=800 emu/cm3, and dipole magnetic layer_2205is made of CoFeTb, has a thickness of 10 nm, and has a magnetization Ms=800 emu/cm3.

As can be seen in graph300, the double SAF (in MRAM200) causes two peaks in the magnetic dipole field (as felt by the free magnetic layer115near −10 nm and 10 nm), and the two peaks are slightly below 5 Oe (Hz˜5 Oe). Also, the double SAF (in MRAM200) causes a dip in the dipole field at 0 nm (center) of the free magnetic layer115, and the dip does not reach −5 Oe (Hz˜−5 Oe).

The MRAM device200(because of the double SAF, i.e., reference magnetic layer250and dipole magnetic layer260) has almost zero local magnetic dipole field (i.e., at each respective radial coordinate) and almost zero average magnetic dipole field on the free magnetic layer115. The average magnetic dipole field is less than 5 Oe.

FIG. 4is a graph400illustrating a waveform405as the magnetic dipole field created by a single SAF in an MRAM device and the waveform305as the magnetic dipole field created by double SAF in the MRAM device200(discussed inFIG. 3).

InFIG. 4, the single SAF (in a similar MRAM to MRAM200but without dipole magnetic layer_1210and dipole magnetic layer_2205) causes two peaks in the dipole field (as felt by the free magnetic layer near −10 nm and 10 nm), and the two peaks are approximately 300 Oe (Hz˜300 Oe). Also, the single SAF causes a dip in the dipole field at 0 nm (center) of the free magnetic layer, and the dip is approximately −300 Oe (Hz˜−300 Oe).

As compared to the single waveform405, the double SAF waveform305has very little magnetic dipole field effect on the free magnetic layer115. This small magnetic dipole field disturbs the free magnetic layer115less, making free magnetic layer115switch more like a single magnetic domain.

Now turning toFIG. 5, a method500of forming a magnetic random access memory (MRAM) device200is provided according to an embodiment. At block505, the free magnetic layer115is provided. At block510, first fixed layers (e.g., reference magnetic layer_1215and reference magnetic layer_2220) are disposed above the free magnetic layer115. At block515, second fixed layers (e.g., dipole magnetic layer_1210and dipole magnetic layer_2205) are disposed below the free magnetic layer115. At block520, the first fixed layers (e.g., reference magnetic layer_1215and reference magnetic layer_2220) and the second fixed layers (e.g., dipole magnetic layer_1210and dipole magnetic layer_2205) both comprise a rare earth element (e.g., one or more rare earth elements).

The first fixed layers (e.g., reference magnetic layer_1215and reference magnetic layer_2220) and the second fixed layers (e.g., dipole magnetic layer_1210and dipole magnetic layer_2205) both comprise a transition metal in addition to the rare earth element. The transition metal includes at least one of Co, Fe, and Ni. The rare earth element includes at least one of Tb, Gd, and/or europium (Eu).

The first fixed layers (e.g., reference magnetic layer_1215and reference magnetic layer_2220) and the second fixed layers (e.g., dipole magnetic layer_1210and dipole magnetic layer_2205) comprise at least one of CoFe and Tb multilayers and a CoFeTb alloy.

The first fixed layers and the second fixed layers comprise at least one of CoFe and Gd multilayers and a CoFeGd alloy. The free magnetic layer115is sandwiched between two oxide layers (e.g., the tunnel barrier layer120and oxide seed layer110). The free magnetic layer115is grown on the oxide seed layer110. One side of the free magnetic layer115is adjacent to the oxide seed layer110, and the another side of the free magnetic layer115is adjacent to the tunnel barrier layer120. The first fixed layers (e.g., reference magnetic layer_1215and reference magnetic layer_2220) or the second fixed layers (e.g., dipole magnetic layer_1210and dipole magnetic layer_2205) are adjacent to the tunnel barrier layer120. There may be a case when the layers above and below the free magnetic layer115are reversed.

At least one of the first fixed layers (e.g., reference magnetic layer_1215and reference magnetic layer_2220) and the second fixed layers (e.g., dipole magnetic layer_1210and dipole magnetic layer_2205) comprises a nonmagnetic spacer layer225. Although the dipole magnetic layer_1210and dipole magnetic layer_2205are not shown sandwiching the nonmagnetic spacer layer225, the nonmagnetic spacer layer225may be included in the dipole magnetic layer260.

FIG. 6illustrates an example computer600that can implement features discussed herein. The computer600may include a plurality of spin torque MRAM devices200connected in a grid to form addressable memory cells. One skilled in the art understands how to connect spin torque MRAM devices. The computer600may be a distributed computer system over more than one computer. Various methods, procedures, modules, flow diagrams, tools, applications, circuits, elements, and techniques discussed herein may also incorporate and/or utilize the capabilities of the computer600. Indeed, capabilities of the computer600may be utilized to implement and execute features of exemplary embodiments discussed herein.

Generally, in terms of hardware architecture, the computer600may include one or more processors610, computer readable storage memory620(which may include one or more MRAM devices200, e.g., in an array), and one or more input and/or output (I/O) devices670that are communicatively coupled via a local interface (not shown). The local interface can be, for example but not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface may have additional elements, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Further, the local interface may include address, control, and/or data connections to enable appropriate communications among the aforementioned components.

The processor610is a hardware device for executing software that can be stored in the memory620.

The software in the computer readable memory620may include one or more separate programs, each of which comprises an ordered listing of executable instructions for implementing logical functions. The software in the memory620includes a suitable operating system (O/S)650, compiler640, source code630, and one or more applications660of the exemplary embodiments.

The I/O devices670may include input devices (or peripherals) such as, for example but not limited to, a mouse, keyboard, scanner, microphone, camera, etc. Furthermore, the I/O devices650may also include output devices (or peripherals), for example but not limited to, a printer, display, etc. Finally, the I/O devices670may further include devices that communicate both inputs and outputs, for instance but not limited to, a NIC or modulator/demodulator (for accessing remote devices, other files, devices, systems, or a network), a radio frequency (RF) or other transceiver, a telephonic interface, a bridge, a router, etc. The I/O devices670also include components for communicating over various networks, such as the Internet or an intranet. The I/O devices670may be connected to and/or communicate with the processor610utilizing Bluetooth connections and cables (via, e.g., Universal Serial Bus (USB) ports, serial ports, parallel ports, FireWire, HDMI (High-Definition Multimedia Interface), etc.).