Research led by Osaka University demonstrate magnetic phase diagram of C_sC_uCl₃ by measuring physical properties under multiple extreme conditions

A research group led by Graduate Student Katsuki Nihongi, Assistant Professor Takanori Kida, and Professor Masayuki Hagiwara of the Graduate School of Science at Osaka University, in collaboration with Professor Koichi Kindo and Professor Yoshiya Uwatoko of the Institute of Solid State Physics at the University of Tokyo, Distinguished Professor Katsuya Inoue of the Graduate School of Advanced Science and Engineering at Hiroshima University, Assistant Professor Yusuke Kousaka of the Graduate School of Engineering at Osaka Metropolitan University and Dr. Julien Zaccaro of Institut Néel have succeeded in producing a magnetic phase diagram of the chiral triangular lattice antiferromagnet C_sC_uCl₃ under pressure in a magnetic field range above the saturation field.

The question of what kind of spin arrangement or if spin-liquid state is reached when the interactions between electron spins competes due to geometric frustration has long been debated. Measurements under multiple extreme conditions, where a magnetic field and pressure are applied simultaneously, show promise in providing an edge in solving the problem.

The research group has developed a high-pressure cell made of a nickel-chromium-aluminum alloy with a maximum pressure of 2 gigapascals that can be combined with a high magnetic field generator capable of generating a maximum magnetic field of 55 tesla. In order to observe the magnetization signal associated with the magnetic phase transition, they found a variety of magnetic phases in the chiral triangular lattice antiferromagnet C_sC_uCl₃ under a magnetic field and pressure by using the inductance-capacitance (LC) method, a magnetization measurement technique based on radio wave technology.

Furthermore, by identifying the pressure dependence of the saturated magnetic field (the magnitude of the magnetic field when all spins in the material point toward the magnetic field) that can be observed for the first time under a strong magnetic field of 30 Tesla or more, the numerical calculation results can be compared, and the mechanism in each magnetic phase observed under magnetic field and pressure could be verified by complementary studies of experiments and theories.

The method the research group developed is characterized by its ability to measure phase transition phenomena associated with changes in the magnetic field and temperature in a non-contact manner and can obtain sufficient measurement sensitivity with only a few turns of a detection coil. The coil can be inserted into a narrow space in a pressure cell that generates higher pressure and induce a phase transition driven by quantum fluctuations under pressure, which can be expanded to studies that reveal its physical properties in a high magnetic field.

"In addition to the magnetic material research with magnetic frustration we conducted in our research, antiferromagnetic or ferrimagnetic spintronics materials and chiral magnetic materials that exhibit novel spin textures, such as skyrmions in magnetic fields, can be studied under high magnetic fields and high pressures to create a magnetic field- pressure-temperature phase diagram in a wide space of physical parameters," says Professor Hagiwara. "So, this may lead to the discovery of new physical phenomena and magnetic phases in multiple extreme environments."

■ Geometric frustration: It becomes impossible to determine the direction of remaining spins if any two spins are antiparallel in a triangular lattice antiferromagnet. This term describes the factors that cause such conditions.

Journal Information
Publication: PHYSICAL REVIEW B
Title: Magnetic field and pressure phase diagrams of the triangular-lattice antiferromagnet C_sC_uCl₃ explored via magnetic susceptibility measurements with a proximity-detector oscillator
DOI: 10.1103/PhysRevB.105.184416