Magnetic Phase Transitions in K₂Cu_cMn_1−cF₄ Mixed Crystals

抄録

The magnetic properties of insulating quasi-two-dimensional mixed ferromagentic (F) and antiferromagnetic (AF) system K₂Cu_cMn_1−cF₄ were studied by d.c. and a.c. magnetic susceptibility (χ) measurements, and phase diagram of this system was obtained. AF-region lies in the Cu concentration range of 0≤c<0.5, and F region does in 0.8<c≤1. In the intermediate range (0.5<c<0.8), spin-glass behaviors were observed in a.c.χ and d.c.χ below 1 K. The relatively low spin-glass transition temperature was intepreted to result from the characteristic of quasi-two-dimensional nature of this system. The random-field effects were observed in the AF region, and T_N(c)-, T_c(c)-lines were discussed in relation to the percolation theory and orbital ordering of Cu²⁺ ions.