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Novel Mechanisms of Magnetic Anisotropy and Frustration in a Copper-Iridium Oxide

发布日期:2016-07-28   浏览次数

Novel Mechanisms of Magnetic Anisotropy and Frustration in a Copper-Iridium Oxide

时间:2016年7月27日(星期三)上午10:00信息楼大会议室

Weiguo Yin

Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA

High-temperature superconductivity in the 3d transition-metal compounds (TMCs), such as copper oxides and iron pnictides, and relativistic Mott insulating state in the 5d TMCs, such as iridium oxides, are among the most extensively studied phenomena in condensed matter physics and materials science. We now begin to explore the novel physics in mixed 3d-5d TMCs not present in the pure 3d or pure 5d ones. Its origin lies in the unusual exchange pathways opened by mixed spin-orbit coupling strengths. Such materials could naturally take the form of the double-perovskite-like structure AB1-xB’xO3 or the ABO3/A’B’O3 heterostructure epitaxy films where, for example, B=3d and B’=5d ions. In this talk, we shall use Sr3CuIrO6, the prototypical parent compound of a family of copper-iridium oxides, to illustrate novel mechanisms of magnetic anisotropy and frustration in mixed 3d-5d systems [1,2]. Sr3CuIrO6 is known as a spin one-half chain ferromagnet exhibiting three unexpected phenomena: (i) large spin excitation gap, (ii) small saturation magnetic moment, and (iii) antiferromagnetic Curie-Weiss behavior of the high-temperature magnetic susceptibility despite ferromagnetic exchange interaction. We explain these puzzles using a first-principles derived effective Hamiltonian with alternating g-factors, namely g=2 and –3 on the Cu and Ir ions, respectively. Furthermore, we found an exotic magnetic-field driven critical point at which one half of the spins are frozen into a complete order and the other half are fully disordered at zero temperature. The responses of this new state to external stimuli are also unique.

1. Wei-Guo Yin et al., “Ferromagnetic Anisotropy from Antiferromagnetic Superexchange in the Mixed 3d-5d

Transition-Metal Compound Sr3CuIrO6,” Phys. Rev. Lett. 111, 057202 (2013).

2. Wei-Guo Yin, C. R. Roth, and A. M. Tsvelik, “Magnetic frustration and a ‘half fire, half ice’ critical point from nonuniform g factors,” arXiv:1510.00030 (2016).

 

Weiguo Yinghao教授简历:

Weiguo Yin

Condensed Matter Theory Group

Condensed Matter Physics and Materials Science Division

Brookhaven National Laboratory, Upton, New York 11973, USA

Phone: (631) 344-2150 Fax: (631) 344-2739 Email: wyin@bnl.gov

Research Interest:

- Theories for strongly correlated and complex systems

First-principles guided modeling, developing new methods and algorithms and materials

Education:

- PhD in Theoretical Condensed Matter Physics, Nanjing University, China 1998

- MS in Theoretical Condensed Matter Physics, Nanjing University, China 1994

- BS in Theoretical Physics, Nanjing University, China 1991

Employment:

- Physicist, Brookhaven National Laboratory, USA 2011-

- Associate Physicist, Brookhaven National Laboratory, USA 2008-2011

- Assistant Physicist, Brookhaven National Laboratory, USA 2006-2008

- Research Associate, Brookhaven National Laboratory, USA 2004-2006

- Research Associate, University of Nebraska at Omaha, USA 2001-2004

- CUHK Fellow, Chinese University of Hong Kong, Hong Kong 2000-2001

- Postdoctoral Fellow, Fudan University, Shanghai, China 1998-2000

Awards and Honors:

- National Outstanding PhD Dissertation Award of China 2000