Physics Department News

Oxides containing 5d ions, particularly Ir4+, offer possibilities for interesting spin-orbit and spin-lattice coupling effects. In these materials, the energy scales for spin-orbit interactions, Coulomb repulsion, and crystalline-electric fields can be very similar. Competition between these three energies can result in exotic magnetic states such as spin-orbit entanglement, extreme magnetic exchange anisotropy leading to, for example, a Kitaev spin liquid, and spin-orbit entangled Mott insulating behaviour. Using experiments performed at the National High Magnetic Field Laboratory, a team from the USA, UK and South Korea (including Paul Goddard at Warwick) have observed extremely large coercive magnetic fields of up to 55 T in Sr3NiIrO6 and 52 T in Sr3CoIrO6, with switched magnetic moments ≈ 1 μ_B and 3 μB per formula unit, respectively. Rather than the switching of magnetic domains, which is the cause of the coercive fields of traditional ferromagnets, the large hysteresis observed in our materials evolves out of a frustrated, antiferromagnetic ground state that incorporates an entangled spin-orbit state on the 5d ion.

• Caption to Figures: Model for the behaviour of the low-temperature magnetization of Sr3NiIrO6.
• Publication: Phys. Rev. B 94, 224408 (2016)
• DOI: 10.1103/PhysRevB.94.224408