# Presentation: 559144

## Nanoscale Spin Transfer Devices and MaterialsAndrew D. Kent, New York University, DMR-0405620

- An electric current flow through small magnets can transport spin angular momentum and dramatically affect the magnets, even changing their magnetization direction. As much information is stored in magnetic materials (such as, in hard disk drives) this phenomena, once better understood and controlled, may lead to ultra-fast and high density memories. A bottleneck to research progress has been the fabrication of magnetic materials which are less than 100 nm in lateral size with electrical contacts. With Dr. Sun at IBM Research, we are using a new nanostencil substrate method that enables the rapid prototyping of devices and materials. Experiments are in progress to establish the factors that determine the current necessary to change the magnetization direction and the efficiency of spin-transfer.

- First an array of undercut stencils are fabricated.

- Left: Then the desired layered structure is grown by evaporation of material onto the stencil. Right: Cross-sectional transmission electron microscopy image.
- Sufficient material is added to fill-up the stencil producing electrical contact to the top and bottom of the nanopillar.

***Cu***

***Co***

***Co***

***I***

- 100 nm

*Physics Review Letters ****93****, 176604 (2004)*
*Physical Review B ****71****, 140403 (2005)*
- Additional information available at:
- http://www.physics.nyu.edu/kentlab/

**Notes:**
It is well known that an electric current can affect a magnetic material and vice-versa. This is the basis for electric motors and generators.  A current in a wire produces a magnetic field that can exert a force on a nearby magnet. This magnetic field is associated with the flow of charge, due to electrons moving in the wire. For example, a compass needle (which is nothing more than a magnetic material in the shape of a needle) placed close to the wire can be deflected by the current-induced magnetic field. This was realized over 150 years ago. Very recently it was discovered that a current flow directly through a small magnet can exert a much stronger force on the magnet, even changing its magnetization direction. This force arises because electrons have an intrinsic magnetic moment (a spin) in addition to their electrical charge. In a magnetic conductor (like Iron or Cobalt)  the electrons that move are spin-polarized. When they flow they can “move” magnetism from one region of the conductor to another--this has been called spin-transfer, as electron spins are moved from one place to another. This new interaction between a magnet and a current is still poorly understood and experiments on very important to establishing the basic physics. For example, up until early this year, it was thought that two magnetic layers were necessary in order for there to be spin-transfer effects, one layer to create a spin-polarized current and the other to respond to the polarization. Recent experiments in our group have shown that these effects occur even when only one layer in present, the same layer that creates the spin-polarized current responds to the resulting current. This observation is very important to our understanding of spin-transfer as well as device concepts that will use this new interaction. There is also great potential for information processing devices based on this interaction with both improved energy efficient and speed.

## Nanoscale Spin Transfer Devices and MaterialsAndrew D. Kent, New York University, DMR-0405620

**Education**
**Post-doc:** Jean-Marc Beaujour
**Graduate Students:** Wenyu Chen, Barbaros Ozyilmaz (post-doc ,Columbia, 2005).
**Undergraduates: **Mariano Zimmler (graduate student, Harvard, Fall 2004), Stuart Kirschner (graduate student, Johns Hopkins, Fall 2005), Brian Hayes, Lorraine Robinson, Alexandra Fries, James Lee and James Pyun
**High School Student**: Yuriy Kagan, Intel Science Research (Columbia, Fall 2004)
**Societal Impact**
**	****Research of fundamental importance and critical to future magnetic information storage technology.**

- Kent group at NYU involved in spin-transfer studies. Pictured above (left-right): Wenyu Chen, Andrew Kent, Barbaros Ozyilmaz, Jan Larsen,  Jean-Marc Beaujour and Mariano Zimmler