Ferromagnetic ordering of linearly coordinated Co ions in LiSr2[CoN2]

LiSr2[CoN2] single crystals were successfully grown out of Li-rich flux. Temperature- and field-dependent measurements of the magnetization in the range of T=2–300K and up to μ0H=7T as well as measurements of the heat capacity are presented. Ferromagnetic ordering emerges below TC=44K and comparatively large coercivity fields of μ0H=0.3T as well as pronounced anisotropy are observed upon cooling. Polycrystalline samples of the Ca analog LiCa2[CoN2] were obtained and investigated in a similar way. In both compounds Co manifests orbital contributions to the magnetic moment and large single-ion anisotropy caused by second-order spin-orbit couplings. Quantum chemistry calculations reveal a magnetic anisotropy energy of 7 meV, twice as large as the values reported for similar Co d8 systems.