# Presentation: 520023

## Below a temperature of 256 oC (17 K), a novel state of matter is realized in the material URu2Si2. 

- Below a temperature of 256 oC (17 K), a novel state of matter is realized in the material URu2Si2.
- Understanding this state is not only an intellectual challenge, but could also lead to the prediction of new materials with unprecedented characteristics and potential applications.
- Our nuclear magnetic resonance (NMR) measurements using single crystals, random, and oriented powders of this material are helping scientists elucidate the nature of this “hidden order”.** **
**The NMR spectra shown at right were taken as part of this project. They represent evidence for an internal magnetic field in the hidden order state; i.e., as a shift of the distribution center for low temperatures****.**

**Probing Hidden Order and Magnetic Disorder in Correlated Electron Systems Using Spin Probes, O. Bernal, Cal State LA, DMR-0203524**

**NMR Roster at CSULA Physics Between 2002—2005: **
*** Alhambra High School (2)**
-    **-James Luo     -Adrian Chan**
*** CSULA undergraduates (6)**
-   **-Odet Bonilla       -Chris Rodriguez **
**  ****-Fred Warnecke  -Kyle Irwin **
**  ****-Dawit Haile****     ****     -Deepa Patil**
*** CSULA graduates ( 2 MS):**
-    **-Seunghun Jung**  **-Mike Moroz**

**Notes:**
Understanding the nature of the hidden order state in novel materials such as URu2Si2 might open the doors to new and unexpected technological applications as well as innovative methods of control and device design. For the first time in the history of this material (which was discovered in 1985), there is compelling evidence to associate an internal magnetic field with the hidden order state. The measurement of this internal field in single crystals has been possible through careful NMR experimentation carried out by the PI and his undergraduate and masters students at CSULA, together with an ongoing collaboration between the PI and scientists at the National High Magnetic Field Lab in Tallahassee. These experiments have been possible thanks to continuous funding by the NSF. Of considerable importance is the fact that carefully planned and long-lasting experiments are required to obtain data of this quality. The NMR group at CSULA’s Physics Department is, so far, the only team in the world carrying out these single-crystal NMR experiments to fruition. They demand patience and a long-range research plan designed to facilitate the discovery of new phenomena associated with the hidden order state. Not many groups in the world engage in long-term efforts of this kind. Measurement of an internal field below the hidden order state temperature is an important result because, of the many theories that have been developed to describe the hidden order, only two would be compatible with the presence of an internal field. After about twenty years of research, there are currently three specific theories which can be said to explain most of the properties of the hidden order: quadrupolar order, octupolar order, and orbital antiferromagnetism. The NMR experiments carried out under this project rule out quadrupolar order, for which no internal magnetic field is predicted, leaving only either octupolar order or orbital antiferromagnetism as the possible candidates for hidden order. We have, so far, published four papers addressing the issue of hidden order in URu2Si2: “Hidden and Magnetic Order in Powdered URu2Si2 Found by NMR at Ambient Pressure”, Physica B; “Ambient Pressure NMR in URu2Si2: Internal-Field Anisotropy”, Journal of magnetism and Magnetic Materials; “URu2Si2: NMR Linewidth below TN”, Physica B; “29Si NMR and Hidden Order in URu2Si2”, Physical Review Letters. One other paper has been recently submitted for publication and one more is in preparation.

## Probing Hidden Order and Magnetic Disorder in Correlated Electron Systems Using Spin Probes, O. Bernal, Cal State LA, DMR-0203524

- Understanding the nature of the hidden order state in novel materials such as URu2Si2 might open the doors to new and unexpected technological applications as well as innovative methods of control and device design. For the first time in the history of this material (which was discovered in 1985), there is compelling evidence to associate an internal magnetic field with the hidden order state. The measurement of this internal field in single crystals has been possible through careful NMR experimentation carried out by the PI and his undergraduate and masters students at CSULA, together with an ongoing collaboration between the PI and scientists at the National High Magnetic Field Lab in Tallahassee. These experiments have been possible thanks to continuous funding by the NSF. Of considerable importance is the fact that carefully planned and long-lasting experiments are required to obtain data of this quality. The NMR group at CSULA’s Physics Department is, so far, the only team in the world carrying out these single-crystal NMR experiments to fruition. They demand patience and a long-range research plan designed to facilitate the discovery of new phenomena associated with the hidden order state. Not many groups in the world engage in long-term efforts of this kind. Measurement of an internal field below the hidden order state temperature is an important result because, of the many theories that have been developed to describe the hidden order, only two would be compatible with the presence of an internal field. After about twenty years of research, there are currently three specific theories which can be said to explain most of the properties of the hidden order: quadrupolar order, octupolar order, and orbital antiferromagnetism. The NMR experiments carried out under this project rule out quadrupolar order, for which no internal magnetic field is predicted, leaving only either octupolar order or orbital antiferromagnetism as the possible candidates for hidden order. We have, so far, published four papers addressing the issue of hidden order in URu2Si2: “Hidden and Magnetic Order in Powdered URu2Si2 Found by NMR at Ambient Pressure”, Physica B; “Ambient Pressure NMR in URu2Si2: Internal-Field Anisotropy”, Journal of magnetism and Magnetic Materials; “URu2Si2: NMR Linewidth below TN”, Physica B; “29Si NMR and Hidden Order in URu2Si2”, Physical Review Letters. One other paper has been recently submitted for publication and one more is in preparation.

## NSF funding of this and previous projects has been important in allowing our group to recruit and train undergraduate and masters level students in the workings of low-temperature physics and magnetic resonance techniques since 1998. 

- The availability of funds for research and education endeavors has also facilitated the beginnings of a collaboration involving  the training and coaching of K-12 science teachers in the LA area. A major goal of this effort is to increase awareness of science and technology and to develop tools and assistance for the improvement    of science teaching at the K-12 levels.
**At right are pictures of the first field trip to CSULA by (60) students from Allesandro Elementary School in Los Angeles (3rd to 6th grade). High school students are also involved in our research.**

**Probing Hidden Order and Magnetic Disorder in Correlated Electron Systems Using Spin Probes, DMR-0203524**

**Probing Hidden Order and Magnetic Disorder in Correlated Electron Systems Using Spin Probes, O. Bernal, Cal State LA, DMR-0203524**