FY2020 Annual Report


Electronic and Quantum Magnetism Unit
Associate Professor Yejun Feng



This is the fourth year of the Electronic and Quantum Magnetism Unit at OIST. 

1. Staff & Students

  • Anjana Krishnadas, Graduate Student
  • Magarita Dronova, Graduate Student
  • Dr. Yajian Hu, Postdoc Researcher
  • Scott Cooper, Technical Staff
  • Dr. Mykola Medvidov, Technical Staff
  • Yukiko Murabayashi, Administrative Assistant
  • Jaime Rivera, Intern 
  • Roman Muhkin, Intern
  • Tomoyuki Murata,Visiting research student from Univ. of The Ryukyus
  • Dr. Xiang Li, Visiting Postdoc from Caltech
  • Prof. Yoshitomo Karaki, Visiting Researcher, from Univ. of The Ryukyus

2. Collaborations

2.1 Synchrotron x-ray magnetic diffraction under high pressure

  • We use the resonant x-ray magnetic diffraction to study the all-in-all-out antiferromagnetic order in Sm2Ir2O7 and Eu2Ir2O7, under continous pressure tuning to a quantum critical point. 
  • Collaborators:
    • Dr. Yishu Wang, Institute for Quantum Matter, Johns Hopkins University
    • Professor Thomas Rosenbaum, Caltech
    • Professor Andrew Boothroyd, University of Oxford
    • Professor Satoru Nakatsuji, University of Tokyo

2.2 Continuous Metal-insulator transition driven by spin correlations

  • We discovered a continuous metal-insulator transition in Cd2Os2O7 through Hall coefficient measurement, when the effect of domain wall conductance is removed. 
  • Collaborators:
    • Dr. Yishu Wang, Institute for Quantum Matter, Johns Hopkins University
    • Professor David Mandrus, University of Tennessee 
    • Professor Patrick Lee, MIT
    • Professor Thomas Rosenbaum, Caltech

2.3 Optical Raman scattering under high pressure and low temperature

  • We focus on magnon Raman scattering to explore magnetic quantum phase transitions in Sr2IrO4.
  • Collaborators:
    • Dr. Xiang Li, Caltech
    • Anjana Krishnadas, OIST
    • Professor David Hsieh, Caltech
    • Professor Thomas Rosenbaum, Caltech

2.4 Single crystal growth of spinel magnets

  • We grow spinel magnets in the single crystal form and study their quality through a series of techniques including magnetic susceptibility, heat capacity, and neutron diffraction.
  • Collaborators:
    • Dr. Feng Ye, ORNL, USA
    • Dr. Christina Hoffmann, ORNL, USA
    • Prof. Yoshinori Okada, OIST

3. Activities and Findings


3.1 X-ray magnetic diffraction under high pressure

Our work on Sm2Ir2O7 was published at Physical Review B: Rapid Communications as an Editor's Suggestion. 

3.2 Optical Raman scattering under high pressure

Visiting Postdoc Dr. Xiang Li published a paper on Review of Scientific Instruments about the high-pressure Raman scattering instrument. 

3.3 Single crystal growth using high temperature solution technique

Margarita Dronova is leading the effort on single crystal growth of spinel magnets and taking effort on the subsequent charcterization process. Scott Cooper assists with electronic and mechanical instrument development for the growth apparatus. This work is in collaboration with staffs at the Spallation Neutron Source at Oak Ridge National Laboratory. 


4. Publications

4.1 Journals

Xiang Li, S. E. Cooper, A. Krishnadas, D. M. Silevitch, T. F. Rosenbaum, Yejun Feng, Optical Raman measurements of low frequency magnons under high pressure. Rev. Sci. Instrum. 91, 113902 (2020).

Yishu Wang, T. F. Rosenbaum, D. Prabhakaran, A. T. Boothroyd, Yejun Feng, Approaching the quantum critical point in a highly-correlated all-in-all-out antiferromagnet. Phys. Rev. B 101, 220404(R) (2020), as an Editor’s Suggestion.

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

Invited talks by the PI:

Nothing to report

Contributed talks with the PI listed:

Nothing to report

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

Nothing to report

7. Other

Nothing to report.