Pressure Effect on the Transport and Magnetic Properties for the Hole-Doped Delafossite Oxide CuCr_0.97Mg_0.03O₂ Having an S = 3/2 Antiferromagnetic Triangular Sublattice

Abstract

We investigated an effect of hydrostatic pressure (P) up to 14 GPa on a resistivity () of a hole-doped delafossite oxide CuCr 0:97 Mg 0:03 O 2 having an S ¼ 3=2 antiferromagnetic (AF) triangular sublattice. In contrast to a nonmonotonic P-dependence of , an AF transition temperature (T N % T peak ) deduced from a peak temperature (T peak ) of a temperature dependence of local activation energy monotonically increases with the increase of P. The monotonic increase of T peak without a large change of mainly comes from an enhancement of an overlap between neighboring 3d orbitals of Cr ions, which suggests that the intrinsic effect of itinerant hole on T N in CuCrO 2 must be more dramatic than the observed one of the Mg substitution accompanying negative chemical pressure.

Effects of Mg, Ag, and Al Substitutions on Magnetic Excitations in the Triangular-Lattice Antiferromagnet CuCrO2

“…One of the plausible origins of the above changes in the magnetic excitations is a change in the crystal structure induced by the 3% substitution of Mg, where the lattice constants show 0.2-0.3% increase. 4 However, the increase of the lattice constants should decrease the antiferromagnetic exchange interactions, 19 which is inconsistent with the slight increase of T N by the Mg substitution, 5 and suggests that the the change in the crystal structure has little effect on the magnetic exchange interactions. On the other hand, the Mg substitution increases the magnetization and induces negative magnetoresistance effect, which were attributed to a coupling between doped holes and the Cr spins.…”