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Title: Phase transitions in a quasi-two-dimensional XY random magnetic system

Journal Article · · Phys. Rev. B: Condens. Matter; (United States)

The phase transitions of a randomly mixed quasi-two-dimensional antiferromagnet and ferromagnet Rb/sub 2/Mn/sub 1-//sub x/Cr/sub x/Cl/sub 4/ have been studied experimentally using ac susceptibility (chi), magnetization, and neutron scattering techniques. A characterization of the single crystals of Rb/sub 2/Mn/sub 1-//sub x/Cr/sub x/Cl/sub 4/ grown for this study is made with ac chi and electron-spin-resonance measurements. It turns out that the mixed system is a typical example of an XY magnet in the concentration range 0.1approx. <1.0. The concentration versus transition-temperature (x-T) phase diagram of this alloy under zero external magnetic field is constructed. The transition temperature from the paramagnetic (PM) to the antiferromagnetic phase decreases rapidly with increasing Cr concentration. A transition from the PM phase to the spin-glass (SG) phase is observed in the concentration region 0.34less than or equal tox<0.5. The mixed crystals with the concentrations 0.50less than or equal tox<1.0 show a reentrant spin-glass (RSG) transition; a sequence of transitions from the PM to ferromagnetic (FM) phase and from the FM phase to SG at a lower temperature. Qualitatively, the x-T phase diagram of Rb/sub 2/Mn/sub 1-//sub x/Cr/sub x/Cl/sub 4/ is explained by the theories on competing exchange interactions. The RSG transition is discussed in the context of recent theories on the two-dimensional XY spin glass.

Research Organization:
The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-01, Japan
OSTI ID:
5677777
Journal Information:
Phys. Rev. B: Condens. Matter; (United States), Vol. 37:1
Country of Publication:
United States
Language:
English