Correlation between magnetoresistivity and magnetic entropy change in the 3D-Heisenberg ferromagnet CuCr_2Te_4

摘要

We report a correlation between magnetoresistivity [Δp_(mag) =ρ_(mag){H,T)-ρ_(mag)(0,T)] and magnetic entropy change [ΔS_M = S_M(H,T) - S_M(0,T)] in the metallic spinel CuCr_2Te_4 which orders ferromagnetically below T_C = 320 K. We find that Δp_(mag) =KΔS_M for several temperatures around T_C with a temperature independent K, which suggests that magnetoresistivity arising from the suppression of spin disorder scattering scales with ΔS_M. However, unlike expected theoretically, a clear correlation is not obtained between Δp_(mag) and square of the reduced magnetization (MIM_(sat))~2, where M_(sat) is saturation magnetization at OK. A maximum magnetoresistance of -3.56% for μ_0ΔH = 5T and magnetic entropy change of -1.57 J/kg K occur at T_C, which are typical values for itinerant ferromagnets. Critical exponent analysis using modified Arrott plots yield β = 0.371 ± 0.005 and γ = 1.312 ± 0.02 that are close to the 3D-Heisenberg (β = 0.365, γ = 1.336, and δ = 4.66) model.