Magnetic order, hysteresis and phase coexistence in magnetoelectric LiCoPO${}_4$

Abstract

The magnetic phase diagram of magnetoelectric LiCoPO${}_4$ is established using neutron diffraction and magnetometry in fields up to 25.9T applied along the crystallographic $b$-axis. For fields greater than 11.9T the magnetic unit cell triples in size with propagation vector Q = (0, 1/3, 0). A magnetized elliptic cycloid is formed with spins in the $(b,c)$-plane and the major axis oriented along $b$. Such a structure allows for the magnetoelectric effect with an electric polarization along $c$ induced by magnetic fields applied along $b$. Intriguingly, additional ordering vectors Q $\approx$ (0, 1/4, 0) and Q $\approx$ (0, 1/2, 0) appear for increasing fields in the hysteresis region below the transition field. Traces of this behavior are also observed in the magnetization. A simple model based on a mean-field approach is proposed to explain these additional ordering vectors. In the field interval 20.5-21.0T, the propagation vector Q = (0, 1/3, 0) remains but the spins orient differently compared to the cycloid phase. Above 21.0T and up until saturation a commensurate magnetic structure exists with a ferromagnetic component along $b$ and an antiferromagnetic component along $c$.

References in corpus (5)

• Towards a microscopic theory of toroidal moments in bulk periodic crystals
• Longitudinal SDW order in a quasi-1D Ising-like quantum antiferromagnet
• Field-induced magnetic phases and electric polarization in LiNiPO4
• Anomalous spin-waves and the commensurate-incommensurate magnetic phase transition in LiNiPO4
• Hybrid excitations due to crystal-field, spin-orbit coupling and spin-waves in LiFePO${}_4$

Cited by in corpus (3)

• Symmetry analysis of current-induced switching of antiferromagnets
• Dzyaloshinskii-Moriya interaction and the magnetic ground state in magnetoelectric LiCoPO${}_4$
• High-magnetic field phase diagram and failure of magnetic Grüneisen scaling in LiFePO${}_4$