Large Magnetocrystalline Anisotropy and Giant Coercivity in the Ferrimagnetic Double Perovskite Lu₂NiIrO₆

Abstract

We discover that large uniaxial magnetocrystalline anisotropy driven by the simultaneous presence of spin–orbit coupling and structural distortions is the origin of the giant coercivity observed experimentally in the double perovskite Lu2NiIrO6. The magnetic easy axis turns out to be the monoclinic b-axis with an anisotropy constant as high as 1.9 × 108 erg/cm3. The predicted coercive field of 50 kOe and Curie temperature of 220 K agree with the experimentally observed values and point to potential of Lu2NiIrO6 in spintronics applications. We find that the spin–orbit coupling induces a rare Ir4+ J eff = 1/2 Mott insulating state, suggesting that Lu2NiIrO6 provides a playground to study the interplay between spin–orbit coupling and electronic correlations in a 5d transition metal oxide. The spin–orbit coupling also results in a direct band gap with the valence and conduction states localized on different transition metal sublattices, i.e., efficient electron–hole separation upon photoexcitation and low electron–hole recombination.

Giant coercivity and spin clusters in high pressure polymorphs of Mn2LiReO6.

“…The higher-pressure polymorph crystallises with a P2 1 /n DPv structure with a = 5.2396(5) Å, b = 5.3916(5) Å, c = 7.6480 (7) Å and b = 89.92(1)1 cell parameters. Rietveld refinements confirm full occupancy without any antisite mixing, tested for both B/B 0 and A/B sites, in agreement with the large charge/size mismatches.…”

“…For instance, in single crystals of LuFe 2 O 4 giant coercivity values of 9 T and 11 T at 4 K were reported. 6,7 The orbital magnetic moment of Fe 2+ , as a source of uniaxial magnetocrystalline anisotropy and the collective freezing of ferrimagnetic bidimensional domains are responsible for such values. It is thus imperative to establish if SOC is a requirement or not in order to observe giant coercivities in oxides.…”

Interplay between spin–orbital coupling and electron-correlation: induction of phase transitions and giant magnetic anisotropy in strained LaSr1−xCaxNiReO6

“…Moreover, it has already been well established that the MAE value also substantially depends on the structural distortions. 11,12 As the Ni–O–Ir bond angle moves away from 180° like 151°, 149°, 142°, 141°, and 139.5°, the MAE values increased to 6, 12, 20, 22, and 27 meV in Ln 2 NiIrO 6 (Ln = La, Nd, Eu, Gd, and Lu) DPO, respectively. This means that large structural distortions need more energy to stabilize the system, which results in higher MAE amplitude.…”

“…It is also established that the MAE magnitude increases due to enhancement in the structural distortions. 11 Therefore, a substantial amplitude of the MAE constant (K i ) of 1.9 Â 10 8 erg cm À3 is predicted in the Lu 2 NiIrO 6 motif due to large structural distortion (average Ni-O-Ir bond angle is 1361, which shows larger distortion as compared to other previously reported 3d-O-5d bond angles in DPOs 11,12 ). Ferreira et al 12 proved that the increase in M-O-Ir (M = Mg and Ni) bond angle magnitude (i.e., moving towards 1801) in Ln 2 MIrO 6 DPO reduces the structural distortion, which results in the decrease of the MAE value.…”

“…6,7 It is observed that HM behavior in Re-based DPO is also strongly influenced by SOC associated anisotropy. [8][9][10] Recently, Udo et al 11 found uniaxial magnetocrystalline anisotropy energy (MAE) having the b-axes as the easy magnetization axes and colossal remanence in Lu 2 NiIrO 6 due to the presence of robust SOC and structural distortions, respectively. In addition, it is found that SOC is also responsible for the direct energy bandgap (E g ) in different TM sublattices, which is beneficial for electron-hole separation and recombination.…”