Tricritical phenomenon and H−T phase diagram in a single crystal of the double-perovskite iridate La2ZnIrO6

We report a detailed study of magnetic properties in double perovskite iridate La2ZnIrO6 single crystal, which exhibits an antiferromagnetic (AFM) ground state. The field- and angle-dependent magnetizations [M(H) and M(φ)] suggest strong magnetic anisotropy in this system. The magnetization of La2ZnIrO6 is isotropic in the ab plane, while it is much stronger than that along the c axis. A field-induced magnetic transition from AFM to ferromagnetic (FM) state is found, which is of a first-order type. The critical behavior is investigated, where critical exponents β=0.2317(1),γ=0.9783(2), and δ=5.0071(5) are obtained. The critical exponents belong to the universality class of the tricritical mean-field model, which indicates a field-induced tricritical phenomenon. Based on the scaling equations, we construct the H−T phase diagram for La2ZnIrO6 single crystal with H//b. A tricritical point is revealed at the intersection point between the AFM, FM, and paramagnetic phases (Ttr≈8 K; Htr≈170 Oe).