Yongcheng Zhang

Large E-field tunability of microwave ferromagnetic properties in Fe59.3Co28.0Hf12.7/PZN-PT multiferroic composites

Strong converse magnetoelectric coupling was observed in a multiferroic heterostructure of Fe59.3Co28.0Hf12.7 film on (011) cut lead zinc niobate-lead titanate (PZN-PT) slab, which exhibited a large electric field (E-field) tunability of microwave magnetic properties. With the increase of E-field from 0 to 6 kV/cm on PZN-PT, the ferromagnetic resonance (FMR) field Hr shifts downwards by 430.7 Oe along [011¯] direction and upwards by 492.9 Oe along [100] direction of the PZN-PT. Accordingly, the strong magnetoelectric coupling led to a significantly enhanced self-biased FMR frequency from 4.2 to 7.9 GHz under zero bias magnetic field, and the magnetic damping constant α was decreased from 0.0260 to 0.0185 at the same time. These features demonstrate that this multiferroic laminate is promising in fabrication of E-field tunable microwave components.

Scaling behavior of dynamic hysteresis in relaxor ferroelectric 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 ceramics

The scaling behaviors of dynamic ferroelectric hysteresis in the relaxor ferroelectric 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (PMNT67/33) ceramics near the morphotropic phase boundary (MPB) and other PMNT systems out of MPB region were investigated. The scaling relation of hysteresis area 〈A〉 against frequency f and field amplitude E0 for minor loops takes the form of 〈A〉∝f−0.2391E04.8779; while for the saturated loops, it is 〈A〉∝f 0.0401E00.5722. The scaling relations of PMNT67/33 ceramics are significantly different from those of other ferroelectrics, and the results of the analysis indicate that domain reversal in it is much more sensitive to the change of E0 at low electric field and responses more quickly to f at high electric field than other normal ferroelectrics. The coexistence of rhombohedral (R), monoclinic (M) and tetragonal (T) phases near the MPB and the polar nanoregions seems to play the key role in the dynamic behavior of the domain reversal in relaxor PMNT67/33 ceramics.

Quasi magnetic isotropy and microwave performance of FeCoB multilayer laminated by uniaxial anisotropic layers

A Fe0.7Co0.3-B multilayer was laminated by three Fe0.7Co0.3-B ferromagnetic sublayers prepared by composition gradient sputtering. Three Fe0.7Co0.3-B ferromagnetic sublayers have their individual directions of uniaxial magnetic anisotropy, and the easy magnetic axis of neighboring sublayer successively rotates 60° in the film plane. It is exciting that a quasi magnetic isotropy was achieved in the designed multilayer with a quasi-isotropic hysteresis loop and quasi-isotorpic ferromagnetic resonance around 3.7 GHz. This omnidirectional multilayer is promising for the application in inductors since the 100% hard-axis excitation is achieved for any shaped inductors.

Three types of dissociated misfit dislocations in epitaxial Ba0.3Sr0.7TiO3 thin films grown on (001) LaAlO3

Three types of dissociated misfit dislocations (MDs) in epitaxial Ba0.3Sr0.7TiO3 thin films grown on (001) LaAlO3 have been studied by high-resolution transmission electron microscopy. First, a MD with b=[101] dissociates into two edge partials and results in the incline of film lattice. Second, a [110] MD is split into two (1/2)[110] partials of mixed character. In the third case, a [110] MD of mixed character is composed of three partials which are reacted with two (1/2)⟨110⟩ stacking faults. Neither of the three types of dissociation reactions has been reported before for MDs in perovskite thin films.