posted on 2021-03-18, 13:36authored byCarsten Albert, Tanita J. Ballé, Franziska A. Breitner, Yulia Krupskaya, Alexey Alfonsov, Ziba Zangeneh, Stanislav Avdoshenko, Mohamed S. Eldeeb, Liviu Hozoi, Aswathi Vilangottunjalil, Erik Haubold, Aliaksei Charnukha, Bernd Büchner, Anton Jesche, Vladislav Kataev
We report the results
of the experimental and theoretical study
of the magnetic anisotropy of single crystals of the Co-doped lithium
nitride Li2(Li1–xCox)N with x = 0.005, 0.01,
and 0.02. It was shown recently that doping of the Li3N
crystalline matrix with 3d transition metal (TM) ions yields superior
magnetic properties comparable with the strongly anisotropic single-molecule
magnetism of rare-earth complexes. Our combined electron spin resonance
(ESR) and THz spectroscopic investigations of Li2(Li1–xCox)N
in a very broad frequency range up to 1.7 THz and in magnetic fields
up to 16 T enable an accurate determination of the energies of the
spin levels of the ground state multiplet Ŝ = 1 of the paramagnetic Co(I) ion. In particular, we find a very
large zero field splitting (ZFS) of almost 1 THz (∼4 meV or
33 cm–1) between the ground-state singlet and the
first excited doublet state. On the computational side, ab
initio many-body quantum chemistry calculations reveal a
ZFS gap consistent with the experimental value. Such a large ZFS energy
yields a very strong single-ion magnetic anisotropy of easy-plane
type resembling that of rare-earth ions. Its microscopic origin is
the unusual linear coordination of the Co(I) ions in Li2(Li1–xCox)N with two nitrogen ligands. Our calculations also evidence
a strong 3d–4s hybridization of the electronic shells resulting
in significant electron spin density at the 59Co nuclei,
which may be responsible for the experimentally observed extraordinary
large hyperfine structure of the ESR signals. Altogether, our experimental
spectroscopic and computational results enable comprehensive insights
into the remarkable properties of the Li2[Li1–x(TM)x]N magnets on the
microscopic level.