Magnetic phase transitions and spin density distribution in the molecular multiferroic GaV${}_4$S${}_8$ system

Abstract

We have carried out neutron diffraction and small angle neutron scattering measurements on a high quality single crystal of the cubic lacunar spinel multiferroic, GaV${}_4$S${}_8$, as a function of magnetic field and temperature to determine the magnetic properties for the single electron that is located on the tetrahedrally coordinated V${}_4$ molecular unit. Our results are in good agreement with the structural transition at 44 K from cubic to rhombohedral symmetry where the system becomes a robust ferroelectric, while long range magnetic order develops below 13 K in the form of an incommensurate cycloidal magnetic structure, which can transform into a Néel-type skyrmion phase in a modest applied magnetic field. Below 5.9(3) K, the crystal enters a ferromagnetic phase, and we find the magnetic order parameter indicates a long range ordered ground state with an ordered moment of 0.23(1) ${\mu }_{\mathrm{B}}$ per V ion. Both polarized and unpolarized neutron data in the ferroelectric-paramagnetic phase have been measured to determine the magnetic form factor. The data are consistent with a model of the single spin being uniformly distributed across the V${}_4$ molecular unit, rather than residing on the single apical V ion, in substantial agreement with the results of first-principles theory. In the magnetically ordered state, polarized neutron measurements are important since both the cycloidal and ferromagnetic order parameters are clearly coupled to the ferroelectricity, causing the structural peaks to be temperature and field dependent. For the ferromagnetic ground state, the spins are locked along the $[1,1,1]$ direction by a surprisingly large anisotropy.

References in corpus (14)

• Assessing the Performance of Recent Density Functionals for Bulk Solids
• Néel-type skyrmion lattice in tetragonal polar magnet VOSe${}_2$O${}_5$
• Orbital physics in transition metal compounds: new trends
• Multiferroicity and skyrmions carrying electric polarization in GaV4S8
• Transition from Mott insulator to superconductor in GaNb${}_4$Se${}_8$ and GaTa${}_4$Se${}_8$ under high pressure
• Spin-orbital Entangled Molecular $j_{\mathrm{eff}}$ States in Lacunar Spinel Compounds
• Characteristics of ferroelectric-ferroelastic domains in N{é}el-type skyrmion host GaV${}_4$S${}_8$
• Polar Dynamics at the Jahn-Teller Transition in Ferroelectric GaV4S8
• On the multiferroic skyrmion-host GaV4S8
• Cycloidally modulated magnetic order stabilized by thermal fluctuations in the Néel-type skyrmion host GaV${}_4$S${}_8$
• Assessing exchange-correlation functional performance in the chalcogenide lacunar spinels GaM${}_4$Q${}_8$ (M = Mo, V, Nb, Ta; Q = S, Se)
• Optically driven collective spin excitations and magnetization dynamics in the Néel-type skyrmion host GaV${}_4$S${}_8$
• Microwave directional dichroism resonant with spin excitations in the polar ferromagnet GaV${}_4$S${}_8$
• Robust cycloid crossover driven by anisotropy in the skyrmion host GaV${}_4$S${}_8$

Cited by in corpus (7)

• Magnetic avalanche of non-oxide conductive domain walls
• Recent Advances in Unconventional Ferroelectrics and Multiferroics
• Quasimolecular $J_{\mathrm{tet}}$=3/2 moments in the cluster Mott insulator GaTa${}_4$Se${}_8$
• Resonating holes vs molecular spin-orbit coupled states in group-5 lacunar spinels
• Investigation of the magnetic ground state of GaV${}_4$S${}_8$ using powder neutron diffraction
• Bond Ordering and Molecular Spin-Orbital Fluctuations in the Cluster Mott Insulator GaTa${}_4$Se${}_8$
• Spin dynamics in the skyrmion-host lacunar spinel GaV4S8