Reversible spin-flop and irreversible metamagneticlike transitions induced by a magnetic field in the layeredGd5Ge4antiferromagnet

Temperature and magnetic field dependencies of the magnetization of single crystal Gd 5 Ge 4 indicate antiferromagnetic coupling along the c direction below 130 K. Both a reversible spin-flop transition when a magnetic field of ∼8.4 kOe is applied along the c direction, and irreversible metamagneticlike transitions when a 20 kOe or greater magnetic field is applied at 4.3 K along any of the three crystallographic axes are observed. Although Gd 3 + ions have negligible single ion anisotropy, the metamagnetic transitions and magnetization of Gd 5 Ge 4 in the ferromagnetic state depend on the crystallographic direction reflecting the anisotropy of the exchange interactions due to the distinctly layered Sm 5 Ge 4 -type crystal structure.