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Register a new userField dependent magnetization of BiFeO3 in ultrathin La0.7Sr0.3MnO3/BiFeO3 superlattice
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We report the observation of field-induced magnetization of BiFeO3 (BFO) in an ultrathin BFO/La0.7Sr0.3MnO3 (LSMO) superlattice using polarized neutron reflectivity (PNR). Our PNR results indicate parallel alignment of magnetization across BFO/LSMO interfaces. The study showed an increase in average magnetization on increasing applied magnetic field at 10K. We observed a saturation magnetization of 110 pm 15 kA/m (~0.8 {mu}B/Fe) for ultrathin BFO layer (~2 unit cell) sandwiched between ultrathin LSMO layers (~ 2 unit cell), which is much higher than the canted moment (0.03 {mu}B/Fe) in the bulk BFO. The macroscopic VSM results on superlattice clearly indicate superparamagnetic behavior typically observed in nanoparticles of manganites.
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First-principles density-functional theory calculations show switching magnetization by 90 degree can be achieved in ultrathin BFO film by applying external electric-field. Up-spin carriers appear to the surface with positive field while down-spin ones to the negative field surface, arising from the redistribution of Fe-t2g orbital. The half-metallic behavior of Fe-3d states in the surface of R phase film makes it a promising candidate for AFM/FM bilayer heterostructure possessing electric-field tunable FM magnetization reversal and opens a new way towards designing spintronic multiferroics. The interface exchange-bias effect in this BFO/FM bilayer is mainly driven by the Fe-t2g orbital reconstruction, as well as spin transferring and rearrangement.
We report neutron diffraction and magnetization studies of the magnetic order in multiferroic BiFeO3. In ferroelectric monodomain single crystals, there are three magnetic cycloidal domains with propagation vectors equivalent by crystallographic symmetry. The cycloid period slowly grows with increasing temperature. The magnetic domain populations do not change with temperature except in the close vicinity of the N{P}eel temperature, at which, in addition, a small jump in magneti- zation is observed. No evidence for the spin-reorientation transitions proposed in previous Raman and dielectric studies is found. The magnetic cycloid is slightly anharmonic for T=5 K. The an- harmonicity is much smaller than previously reported in NMR studies. At room temperature, a circular cycloid is observed, within errors. We argue that the observed anharmonicity provides important clues for understanding electromagnons in BiFeO3.
We report on magnetisation and magneto-capacitance measurements in the Bi1-xLaxFeO3 series for 0 < x < 0.15. We confirm that doping with La reduces the threshold magnetic field Hc for cancelling the magnetic spiral phase, and we show that Hc decreases as the La content increases up to x=0.15, which is the highest concentration for maintaining the non-centrosymmetric rhombohedral structure of BiFeO3. Measurements of the dielectric constant as a function of magnetic field in the series also show a maximum magneto-capacitance for x=0.15.
How the magnetoelectric coupling actually occurs on a microscopic level in multiferroic BiFeO3 is not well known. By using the high-resolution single crystal neutron diffraction techniques, we have determined the electric polarization of each individual elements of BiFeO3, and concluded that the magnetostrictive coupling suppresses the electric polarization at the Fe site below TN. This negative magnetoelectric coupling appears to outweigh the spin current contributions arising from the cycloid spin structure, which should produce a positive magnetoelectric coupling.
In this work, the BiFeO3 (BFO)/SrRuO3 (SRO) heterostructure was fabricated and the anomalous Hall effect (AHE) was investigated the in BFO/SRO. It is found the nonmonotonic anomalous Hall resistivity behavior in BFO/SRO is originated from the inhomogeneous SRO layer instead of the topological Hall effect. It is surprised that the AHE in BFO/SRO structure can be manipulated by ferroelectric polarization of BFO. Moreover, an inhomogeneous phenomenological model has been applied on those structure. Furthermore, the modification of band structure in SRO under ferroelectric polarization was discussed by first principle calculation. The ferroelectric-manipulated AHE suggests a new pathway to realize nonvolatile, reversible and low energy-consuming voltage-controlled spintronic devices.
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