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Magnetocrystalline anisotropy in UMn 2 Ge 2 and related Mn-based actinide ferromagnets

We present magnetization isotherms in pulsed magnetic fields up to 62 Tesla, supported by first principles calculations, demonstrating a huge uniaxial magnetocrystalline anisotropy energy - approximately 20 MJ/m 3 - in UMn 2 Ge 2 . This large anisotropy results from the extremely strong spin-orbit coupling affecting the uranium 5 f electrons, which in the calculations exhibit a substantial orbital moment exceeding 2 μ B . Finally, we also find from theoretical calculations that a number of isostructural Mn-actinide compounds are expected to have similarly large anisotropy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Ferromagnetic superexchange in insulating Cr 2 MoO 6 by controlling orbital hybridization

We report the magnetic and electronic structures of the newly synthesized inverse-trirutile compound Cr 2 MoO 6 . Despite the same crystal symmetry and similar bond-lengths and bond-angles to Cr 2 TeO 6 , Cr 2 MoO 6 possesses a magnetic structure of the Cr 2 MoO 6 type, different from that seen in Cr 2 TeO 6 . Ab-initio electronic structure calculations show that the sign and strength of the Cr-O-Cr exchange coupling is strongly influenced by the hybridization between Mo 4d and O 2p orbitals. This result further substantiates our recently proposed mechanism for tuning the exchange interaction between two magnetic atoms by modifying the electronic states of the non-magnetic atoms in the exchange path through orbital hybridization. This approach is fundamentally different from the conventional methods of controlling the exchange interaction by either carrier injection or through structural distortions.

36 MATERIALS SCIENCE↗