Multistage ordering and critical singularities in Co1-xZnxAl2O4(0 <= x <= 1): Dilution and pressure effects in a magnetically frustrated system

作者：Naka Takashi^*; Sato Koichi; Matsushita Yoshitaka; Terada Noriki; Ishii Satoshi; Nakane Takayuki; Taguchi Minori; Nakayama Minako; Hashishin Takeshi; Ohara Satoshi; Takami Seiichi; Matsushita Akiyuki

来源：Physical Review B, 2015, 91(22): 224412.

DOI：10.1103/PhysRevB.91.224412

We report comprehensive studies of the crystallographic, magnetic, and thermal properties of a spinel-type magnetically frustrated compound, CoAl2O4, and a magnetically diluted system, Co1-xZnxAl2O4. These studies revealed the effects of dilution and disorder when the tetrahedral magnetic Co ion was replaced by the nonmagnetic Zn ion. Low-temperature anomalies were observed in magnetic susceptibility at x < 0.6. A multicritical point was apparent at T = 3.4 K and x = 0.12, where the antiferromagnetic, spin-glass-like, and paramagnetic phases met. At that point, the quenched ferromagnetic component induced by a magnetic field during cooling was sharply enhanced and was observable below x = 0.6. At x similar to 0.6, magnetic susceptibility and specific heat were described by temperature power laws, chi similar to C/T similar to T-delta, in accord with the site percolation threshold of the diamond lattice. This behavior is reminiscent of a quantum critical singularity. We propose an x-temperature phase diagram in the range 0 <= x <= 1 for Co1-xZnxAl2O4. The transition temperature of CoAl2O4 determined from magnetic susceptibility measured under hydrostatic pressure increased with increasing pressure.

• 出版日期2015-6-9