Field-induced anisotropic magnetic phase transitions and tricritical phenomena in GdCr6Ge6

The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr6Ge6induces exotic and abundant electro-magnetic phenomena. In this work, we perform a systematical investigation on critical behaviors and magnetic properties of the single-crystal GdCr6Ge6. The temperature, field, and angle dependence of magnetization unveils strong magnetic anisotropy along the c-axis and isotropic characteristic in the ab-plane. Critical exponents β = 0.252(1), γ =0.905(9), δ = 4.606(3) for H//ab, and β = 0.281(3), γ = 0.991(8), δ = 4.541(5) for H//c are obtained by the modified Arrott plot method(MAP) and critical isotherm(CI) analysis. The determined exponents for both directions are consistent with the theoretical prediction of a tricritical mean-field model. Based on detailed magnetization measurements and universality scaling, comprehensive magnetic phase diagrams of GdCr6Ge6for H//ab and H//c are constructed, which reveal that the external field induces a ferromagnetic(FM) transition for H//ab while a ferrimagnetic(FIM) one for H//c. Two tricritical points are determined for H//ab(11.2 K, 266.3 Oe) and H//c(11.3 K, 3.3 kOe) on the phase diagrams, respectively. The field-induced anisotropic magnetic configurations and multiple phases are clarified, where the moments of Gd and Cr form FM coupling for H//ab while FIM one for H//c via the interaction between Gd and Cr sublattices.