Field-induced metamagnetic transitions in S=3/2 Heisenberg antiferromagnets MCr2O4

Magnetic properties of chromium spinels MCr2O4 (M = Zn, Mg, Cd and Hg) were studied. By increasing the size of A-site cation, spin frustration is gradually relieved due to the enhancement of spin-lattice couplings. We found interesting behavior for CdCr2O4 and HgCr2O4 in their magnetization process. They exhibit first order transition to magnetization plateau phase with one half of full moment of S = 3/2 Cr3+ at 28 T and 10 T for CdCr2O4 and HgCr2O4, respectively. These magnetization plateaux are attributed to formation of three-up and one-down collinear spin arrangement. For HgCr2O4 we observed another transition to ferromagnetic state.