The wasp-waisted hysteresis loop and exchange bias in multiferroic BaNiF4

Abstract

Multiferroic BaNiF4 has been fabricated by hydrothermal method. The bifurcation between zero field cooling (ZFC) and field cooling (FC) temperature dependent magnetization (M-T) curves starts at 150 K, indicating the 2D antiferromagnetic (FM) transition. A further upturn of magnetization has been observed below 68 K in FC M-T curve, corresponding to the emergence of 3D AFM structure. Wasp-waisted hysteresis loop was observed under 130 K, which is explained by that the AFM aligned net spins from the canting of neighboring AFM spins due to Dzyaloshinskii-Moriya interaction can be easily aligned by the magnetic field. Exchange bias effect was detected below 70 K, which has been interpreted by the magnetization pinned by the spontaneous polarization through magnetoelectric coupling.

Peculiarities of magnetic ordering in the S=5/2 two-dimensional square-lattice antimonate NaMnSbO4

“…Such type of the hysteresis was observed for many different magnetic materials: for example, for Dy Quite close for us example with similar type of hysteresis loop has also been observed for 2D multiferroic compound BaNiF 4 [67]. According to the theoretical calculations this system is canted antiferromagnet with weak interaction between different sheets [68], leading to low magnetic ordering temperature and pronounced two-dimensional behaviour.…”

Theoretical study of the magnetic properties of BaNiF$$_4$$

“…As expected, no order is observed between the planes with a two-dimensional Heisenberg Hamiltonian and a local single ion anisotropy. As in the literature the 68.4 K transition has been associated with a 3D ordering [18,22], we added dipolar interactions in order to evaluate if some 3D long-range order can be triggered by them. We estimated their energy contribution using the Hamiltonian :…”

“…Neutron scattering experiments, performed at 4.2 and 77 K, showed that the AFM magnetic order has a propagation vector q M = ( 1 2 , 1 2 , 0) at low temperature [21]. At higher temperatures a broad maximum is observed in the magnetic susceptibility that is sometimes attributed to a two-dimensional ordering [22]. C. Ederer et al [23] predicted the existence of a small canting of the magnetic moments in BaNiF 4 which has its origin in the polar distortion, through a proposed Dzyaloshinskii-Moriya (DM) interaction.…”

Direct Magnetization-Polarization Coupling in BaCuF4

“…Although at first glance the magnetic moment could be seen to be weak, it could be amplified by layerengineering and growing a ferromagnetic layer on the top of it as demonstrated through the exchange-bias effect [48] in [Co/Pd(Pt)]/Cr 2 O 3 [49] and NiFe/h-YMnO 3 (LuMnO 3 ) [50] but also in the Barium-based family of AM F 4 crystals with M = Ni and Mn [51,52]. Therefore, bilayered EB-effect could be combined to bring about a novel electrically-controlled magnetic system based-on BaCuF 4 [48].…”