Spin Glass Behavior and Field Induced Anisotropic Magnetic Ordering in S $=$ 2 Frustrated Spinel GeFe2O4

We report comprehensive studies of magnetic properties of spinel GeFe2O4 by means of magnetic susceptibility and heat capacity measurements on both polycrystalline and single crystalline samples as well as neutron powder diffraction measurements. We find that this system shows a spin-glass ground state with the transition temperature around T \textasciitilde 21 K, in contrast to the static antiferromagnetic order reported in earlier literature. In addition, we reveal a field-induced magnetic ordering, which displays strong magnetic anisotropy character.