Switching of both local ferroelectric and magnetic domains in multiferroic Bi0.9La0.1FeO3 thin film by mechanical force

Cross-coupling of ordering parameters in multiferroic materials by multiple external stimuli other than electric field and magnetic field is highly desirable from both practical application and fundamental study points of view. Recently, mechanical force has attracted great attention in switching of ferroic ordering parameters via electro-elastic coupling in ferroelectric materials. In this work, mechanical force induced polarization and magnetization switching were investigated in a polycrystalline multiferroic Bi0.9La0.1FeO3 thin film using a scanning probe microscopy system. The piezoresponse force microscopy and magnetic force microscopy responses suggest that both the ferroelectric domains and the magnetic domains in Bi0.9La0.1FeO3 film could be switched by mechanical force as well as electric field. High strain gradient created by mechanical force is demonstrated as able to induce ferroelastic switching and thus induce both ferroelectric dipole and magnetic spin flipping in our thin film, as a consequence of electro-elastic coupling and magneto-electric coupling. The demonstration of mechanical force control of both the ferroelectric and the magnetic domains at room temperature provides a new freedom for manipulation of multiferroics and could result in devices with novel functionalities

Topological Phases in Magnonics: A Review

Magnonics or magnon spintronics is an emerging field focusing on generating, detecting, and manipulating magnons. As charge-neutral quasi-particles, magnons are promising information carriers because of their low energy dissipation and long coherence length. In the past decade, topological phases in magnonics have attracted intensive attention due to their fundamental importance in condensed-matter physics and potential applications of spintronic devices. In this review, we mainly focus on recent progress in topological magnonics, such as the Hall effect of magnons, magnon Chern insulators, topological magnon semimetals, etc. In addition, the evidence supporting topological phases in magnonics and candidate materials are also discussed and summarized. The aim of this review is to provide readers with a comprehensive and systematic understanding of the recent developments in topological magnonics.Comment: 17 pages, 12 figure

Structural, electronic and magnetic properties of MnxGa/Co2MnSi (x = 1, 3) bilayers

Directly coupled hard and soft ferromagnets were popularly used as the hybridized electrodes to enhance tunnel magnetoresistance (TMR) ratio in the perpendicular magnetic tunnel junction (pMTJ). In this paper, we employ the density functional theory (DFT) with general gradient approximation (GGA) to investigate the interfacial structure and magnetic behavior of tetragonal Heusler-type MnGa (MG)/L21-Co2MnSi (CMS) Heusler alloy bilayers with the MnGa being D022-MnGa alloy (Mn3Ga) and L10-MnGa alloy (MnGa). The MM-MS_B interface with the bridge (B) connection of MnMn termination (MM) of D022- and L10-MnGa layers to MnSi termination (MS) of CMS layers is found to be most stable in the energy point of view. Also, a strong antiferromagnetic coupling and relatively higher spin polarization can be observed in the MM-MS_B interface. Further, a remarkable potential difference to derive electrons to transfer from MG layer to CMS layer appears at the interface. These theoretical results indicate that the MG/CMS bilayers are promising candidates as coupled composites, and moreover, the D022-MG/CMS bilayer is better than L10-MG/CMS bilayer due to its larger spin polarization and built-in field at the interface

High sensitivity face shear magneto-electric composite array for weak magnetic field sensing

© 2020 Author(s). A magnetic field sensor is designed and fabricated using a piezoelectric face shear mode Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT)/Metglas magneto-electric (ME) composite. An outstanding ME coupling coefficient up to 1600 V/(cm Oe) was experimentally achieved, being ∼50% higher than the value from the extensional PMN-PT/Metglas ME composite with the same volume. The detection limit was found to be 2 × 10-6 Oe for the DC magnetic field, while it was 2 × 10-8 Oe for the AC magnetic field. The sensitivity of the face shear mode PMN-PT/Metglas ME composite is about one order of magnitude higher than that of a 32 extensional mode PMN-PT/Metglas based ME composite in sensing a weak DC magnetic field. A sensing array was also designed based on the ME composite to image weak DC magnetic fields, demonstrating a great potential promising for sensing weak magnetic fields

Terahertz spectra revealing the collective excitation mode in charge-density-wave single crystal LuFe2 O4

We report a low-energy collective excitation mode in charge-ordered multiferroic LuFe2O4 via terahertz time domain spectroscopy. Upon cooling from 300 K to 40 K, the central resonance frequency showed a pronounced hardening from 0.85 THz to 1.15 THz. In analogy to the well-known low-energy optical properties of LuFe2O4, we attributed this emerging resonance to the charge-density-wave (CDW) collective excitations. By using the Drude-Lorentz model fitting, we observe the CDW col-lective mode becomes increasingly damped with increasing the temperature. Furthermore, we analyze the kinks of the CDW collective mode at the magnetic transition temperature, which indicates the coupling of spin order with electric polarization

Strain modulated magnetization and colossal resistivity of epitaxial La2/3Ca1/3MnO3 film on BaTiO3 substrate

A sharp drop in resistance and a magnetization anomaly have been observed in La2/3Ca1/3MnO3 film in zero magnetic field at the BaTiO3 substrate structural phase transition temperature, due to the substrate clamping/strain effect, which is confirmed by Raman scattering. However, the anomalies for both resistance and magnetization were eliminated by a strong external magnetic field. These phenomena indicate that strain can cause colossal resistance and a change in magnetization which resembles the magnetic field effect. The interplay of the external forces (strain and magnetic field) is a good demonstration of the strong coupling between spin and lattice in colossal magnetoresistance materials

Ferroelectric properties of Bi3.25Sm0.75V0.02T2.98O12 thin film at elevated temperature

The ferroelectric behavior in terms of electrical polarization and fatigue and dielectric properties at elevated temperature of the ferroelectric Bi3.25Sm0.75V0.02T2.98O12 thin film fabricated by the pulsed laser deposition method were studied. Its switchable polarization increased at elevated temperature, and the coercive field decreased at the same time due to the strong domain depinning process at higher temperature. This film shows almost a polarization-fatigue-free character at room temperature, but the aggregation and diffusion of the thermally activated long-range oxygen vacancies caused strong domain pinning, and thus a poor fatigue resistance was observed at elevated temperature

Strain modulated magnetization and colossal resistivity of epitaxial La2/3Ca1/3MnO3 film on BaTiO3 substrate

A sharp drop in resistance and a magnetization anomaly have been observed in La2/3Ca1/3MnO3 film in zero magnetic field at the BaTiO3 substrate structural phase transition temperature, due to the substrate clamping/strain effect, which is confirmed by Raman scattering. However, the anomalies for both resistance and magnetization were eliminated by a strong external magnetic field. These phenomena indicate that strain can cause colossal resistance and a change in magnetization which resembles the magnetic field effect. The interplay of the external forces (strain and magnetic field) is a good demonstration of the strong coupling between spin and lattice in colossal magnetoresistance materials