Ferromagnetic Order, Strong Magnetocrystalline Anisotropy, and Magnetocaloric Effect in the Layered Telluride Fe3−δGeTe2

The ternary transition-metal compound Fe3−δGeTe2 is formed for 0 2.9GeTe2 via neutron diffraction, thermodynamic and transport measurements, Mössbauer spectroscopy, and electronic structure calculations. Below TC = 225 K, Fe2.9GeTe2 is ferromagnetically ordered with the magnetic moments of 1.95(5) and 1.56(4) μB at T = 1.5 K, both directed along c, which is the magnetic easy axis. Electronic structure calculations confirm this magnetic structure and reveal a remarkably high easy-axis anisotropy of 4.2 meV/f.u. Mössbauer spectra reveal the magnetic ordering too, although a drastic influence of Fe vacancies on quadrupolar splittings and local magnetic fields has been observed. A moderate magnetocaloric effect with the magnetic entropy change upon the ferromagnetic ordering transition, −ΔS ∼ 1.1 J·kg–1·K–1 at 5 T, is found.