Asymmetric Ferromagnetic Criticality in Pyrochlore Ferromagnet Lu2V2O

Abstract We study the ferromagnetic criticality of the pyrochlore magnet Lu 2 V 2 O 7 at the ferromagnetic transition T C ≈ 70 K from the isotherms of magnetization M ( H ) via an iteration process and the Kouv 7 el-Fisher method. The critical exponents associated with the transition are determined 7 β = 0.32(1), γ = 1.41(1), and δ = 5.38 . The validity of these critical exponents is further verified by scaling all the M ( H ) data in the vicinity of T C onto two universal curves in the plot of M / | e | β versus H / | e | β + γ , where e = T / T C - 1 . The obtained β and γ values show asymmetric behaviors on the T T C and the T > T C sides, and are consistent with the predicted values of 3D Ising and cubic universality classes, respectively. This makes Lu 2 V 2 O 7 a rare example in which the critical behaviors associated with a ferromagnetic transition belong to different universality classes. We describe the observed criticality from the Ginzburg-Landau theory with the quartic cubic anisotropy that microscopically originates from the anti-symmetric Dzyaloshinskii-Moriya interaction as revealed by recent magnon thermal Hall effect and theoretical investigations.