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arXiv · 1505.07196

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

Takashi Naka·Koichi Sato·Yoshitaka Matsushita·Noriki Terada·Satoshi Ishii·Takayuki Nakane·Minori Taguchi·Minako Nakayama·Takeshi Hashishin·Satoshi Ohara·Seiichi Takami·Akiyuki Matsushita
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Abstract

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. Around x = 0.6, magnetic susceptibility and specific heat were described by temperature power laws, chi ~ C/T ~ T-d, 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.

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Takashi Naka, Koichi Sato, Yoshitaka Matsushita, Noriki Terada, Satoshi Ishii, Takayuki Nakane, Minori Taguchi, Minako Nakayama, Takeshi Hashishin, Satoshi Ohara, Seiichi Takami, Akiyuki Matsushita. 2015-05-27. Multistage ordering and critical singularities in Co1-xZnxAl2O4 (0 < x < 1):Dilution and pressure effects in a magnetically frustrated system. https://doi.org/10.1103/physrevb.91.224412

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