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1.
The magnetic exchange between epitaxial thin films of the multiferroic (antiferromagnetic and ferroelectric) hexagonal YMnO3 oxide and a soft ferromagnetic (FM) layer is used to couple the magnetic response of the FM layer to the magnetic state of the antiferromagnetic one. We will show that biasing the ferroelectric YMnO3 layer by an electric field allows control of the magnetic exchange bias and subsequently the magnetotransport properties of the FM layer. This finding may contribute to paving the way towards a new generation of electric-field controlled spintronic devices.  相似文献   

2.
陈爱天  赵永刚 《物理学报》2018,67(15):157513-157513
电场调控磁性能够有效降低功耗,在未来低功耗多功能器件等方面具有巨大的潜在应用前景.铁磁/铁电多铁异质结构是实现电场调控磁性的有效途径,其中室温、磁电耦合效应大的应变媒介磁电耦合是最为活跃的研究领域之一.本文简要介绍在以Pb(Mg_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)O_3为铁电材料的多铁异质结构中通过应变媒介磁电耦合效应对磁性、磁化翻转及磁性隧道结调控的研究进展.首先讨论了多铁异质结构中电场对磁性的调控;之后介绍了电场调控磁化翻转的研究进展及理论上实现的途径;然后简述了电场对磁性隧道结调控的相关结果;最后在此基础上,对多铁异质结构中电场调控磁性及磁性器件进行了总结和展望.  相似文献   

3.
We have measured the optical conductivity of single crystal LuMnO3 from 10 to 45000 cm(-1) at temperatures between 4 and 300 K. A symmetry allowed on-site Mn d-d transition near 1.7 eV is observed to blueshift ( approximately 0.1 eV) in the antiferromagnetic state due to Mn-Mn superexchange interactions. Similar anomalies are observed in the temperature dependence of the TO phonon frequencies which arise from spin-phonon interaction. We find that the known anomaly in the temperature dependence of the quasistatic dielectric constant epsilon(0) below T(N) approximately 90 K is overwhelmingly dominated by the phonon contributions.  相似文献   

4.
A reversal of magnetization requiring only the application of an electric field can lead to low-power spintronic devices by eliminating conventional magnetic switching methods. Here we show a nonvolatile, room temperature magnetization reversal determined by an electric field in a ferromagnet-multiferroic system. The effect is reversible and mediated by an interfacial magnetic coupling dictated by the multiferroic. Such electric-field control of a magnetoelectric device demonstrates an avenue for next-generation, low-energy consumption spintronics.  相似文献   

5.
The equilibrium orientations of magnetic moments that correspond to various values and directions of the biasing field are found in a set of magnetic films with cubic crystalline anisotropy and uniaxial induced anisotropy. The films are coupled by exchange interaction of the antiferromagnetic type. Field intervals are established where noncollinear and bistability states causing orientational phase transitions and hysteresis exist. Ninety degree magnetization switching (per switching cycle) of the magnetic moments of the films, as well as an orientational phase transition of bifurcation character, is discovered. Hysteresis loops for 180° in-plane magnetization switching are constructed.  相似文献   

6.
The dynamic magnetization switching of ferrihydrite nanoparticles has been investigated by a pulsed magnetometer technique in maximum fields Hmax of up to 130 kOe with pulse lengths of 4, 8, and 16 ms. Ferrihydrite exhibits antiferromagnetic ordering and defects cause the uncompensated magnetic moment in nanoparticles; therefore, the behavior typical of magnetic nanoparticles is observed. The dynamic hysteresis loops measured under the above-mentioned conditions show that the use of pulsed fields significantly broadens the temperature region of existence of the magnetic hysteresis and the coercivity can be governed by varying the maximum field and pulse length. This behavior is resulted from the relaxation effects typical of conventional ferro- and ferrimagnetic nanoparticles and the features typical of antiferromagnetic nanoparticles.  相似文献   

7.
A novel platform for microfluidic manipulation of magnetic particles is discussed. The particles are confined by an array of magnetic spin valves with bistable ferromagnetic “ON” and antiferromagnetic “OFF” net magnetization states. The switchable fringing fields near the spin-valve traps can be used to selectively confine or release particles for transport or sorting. Spin-valve traps may be potentially used as magnetic molecular tweezers or adapted to a low-power magnetic random access memory (MRAM) switching architecture for massively parallel particle sorting applications.  相似文献   

8.
The theory of the dynamic remagnetization of a synthetic antiferromagnetic system and magnetic points located on a magnetic substrate in an external magnetic field has been considered. The energies of the equilibrium states of the system have been calculated. The conditions of switching between equilibrium states have been described. The conditions of applicability of this theory have been formulated. It has been shown that the process of remagnetization can be implemented in an inertialess regime, escaping the long-term relaxation of the system to a new equilibrium position with the use of a special shape of the field signal. The possibility of the reduction of the switching field amplitude by varying the pulse duration has been demonstrated.  相似文献   

9.
The multiferroic behaviors of polycrystalline GdMnO3 are investigated by focusing on the ferroelectric response to the spin ordering sequence and external magnetic field. The polarization current shows sensitive response to both the Mn cycloidal spin order and Gd antiferromagnetic (AFM) order. The complicated magnetoelectric behaviors suggest that the Mn cycloidal spin order can be modulated by the Gd AFM order at low temperature via the Gd–Mn spin interaction. Due to the possible disorder and defects in polycrystalline nature, polycrystalline GdMnO3 may accommodate the cycloidal spin order in addition to the A-type AFM order at Mn sites, as illustrated by simulation based on the two-orbit double exchange model and measured hysteresis loops of polarization against magnetic field, indicating the switching of the ferroelectric domains coupled with the magnetic domains in response to magnetic field.  相似文献   

10.
Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes.  相似文献   

11.
We report time-resolved measurements of current-induced reversal of a free magnetic layer in Permalloy/Cu/Permalloy elliptical nanopillars at temperatures T=4.2 K to 160 K. Comparison of the data to Landau-Lifshitz-Gilbert macrospin simulations of the free layer switching yields numerical values for the spin torque and the Gilbert damping parameters as functions of T. The damping is strongly T dependent, which we attribute to the presence of an antiferromagnetic oxide layer around the perimeter of the Permalloy free layer. This adventitious antiferromagnetic oxide can have a major impact on spin-torque phenomena.  相似文献   

12.
The perpendicular exchange bias field, H(EB), of the magnetoelectric heterostructure Cr2O3(111)/(Co/Pt)(3) changes sign after field cooling to below the Néel temperature of Cr2O3 in either parallel or antiparallel axial magnetic and electric freezing fields. The switching of H(EB) is explained by magnetoelectrically induced antiferromagnetic single domains which extend to the interface, where the direction of their end spins controls the sign of H(EB). Novel applications in magnetoelectronic devices seem possible.  相似文献   

13.
Wenyu Huang 《中国物理 B》2022,31(9):97502-097502
Because of the wide selectivity of ferromagnetic and ferroelectric (FE) components, electric-field (E-field) control of magnetism via strain mediation can be easily realized through composite multiferroic heterostructures. Here, an MgO-based magnetic tunnel junction (MTJ) is chosen rationally as the ferromagnetic constitution and a high-activity (001)-Pb(Mg$_{1/3}$Nb$_{2/3}$)$_{0.7}$Ti$_{0.3}$O$_{3}$ (PMN-0.3PT) single crystal is selected as the FE component to create a multiferroic MTJ/FE hybrid structure. The shape of tunneling magnetoresistance (TMR) versus in situ E-fields imprints the butterfly loop of the piezo-strain of the FE without magnetic-field bias. The E-field-controlled change in the TMR ratio is up to $-$0.27% without magnetic-field bias. Moreover, when a typical magnetic field ($\sim \pm 10$ Oe) is applied along the minor axis of the MTJ, the butterfly loop is changed significantly by the E-fields relative to that without magnetic-field bias. This suggests that the E-field-controlled junction resistance is spin-dependent and correlated with magnetization switching in the free layer of the MTJ. In addition, based on such a multiferroic heterostructure, a strain-gauge factor up to approximately 40 is achieved, which decreases further with a sign change from positive to negative with increasing magnetic fields. This multiferroic hybrid structure is a promising avenue to control TMR through E-fields in low-power-consumption spintronic and straintronic devices at room temperature.  相似文献   

14.
The possibility of excitation of NMR signals by an ac electric field in magnetically ordered crystals is discussed. Such signals can be recorded using the time-dependent component of the electric polarization vector. It is assumed that the electric and magnetic characteristics are coupled to each other through magnetoelectric and antiferroelectric interactions. Several types of magnetic structures are analyzed in which these interactions are not forbidden by symmetry. Such structures include two-sublattice single-position ferro-and antiferromagnetic phases in centrosymmetrical crystals, two-sublattice magnetic crystals without a center of symmetry (such as KNiPO4), and four-sublattice antiferromagnetic crystals with three types of antiferromagnetism vectors (such as Cr2O3 and α-Fe2O3).  相似文献   

15.
This paper presents a magnetic force microscopy study of antiferromagnetic ordering along chains of dipole-coupled single-domain permalloy nanomagnets with a variety of shapes. Magnetization reversal processes occur due to antiferromagnetic coupling between the closely spaced dots when an appropriate external magnetic field is applied. The goal of this study was to investigate the switching properties and correlation lengths as a function of nanomagnet geometry. We have found that certain shapes (due to their stronger stray fields) clearly show stronger interaction than others when the chain is demagnetized. In addition we have seen that the performance of the nanomagnets also depends on the method of demagnetization, and this fact must be taken into account when shape engineering is used to design coupled nanomagnet systems for a given application.  相似文献   

16.
The magnetic microstructure and domain wall distribution of antiferromagnetic α-Fe2O3 epitaxial layers is determined by statistical image analyses. Using dichroic spectromicroscopy images, we demonstrate that the domain structure is statistically invariant with thickness and that the antiferromagnetic domain structure of the thin films is inherited from the ferrimagnetic precursor layer one, even after complete transformation into antiferromagnetic α-Fe2O3. We show that modifying the magnetic domain structure of the precursor layer is a genuine way to tune the magnetic domain structure and domain walls of the antiferromagnetic layers.  相似文献   

17.
A model for the pressure and temperature dependence of the magnetic contributions to the Gibbs energy of ferromagnetic and antiferromagnetic elements is presented. These contributions are described by three parameters: (1) a critical temperature which is represented by the Curie temperature for ferromagnetic elements or Néel temperature for antiferromagnetic elements, (2) the pressure dependence of that critical temperature, (3) the average magnetic moment per atom. Using thermal expansion data, all these parameters and consequently the pressure and temperature dependence of the magnetic contribution can be calculated. Nickel, a ferromagnetic element, is used as an example.  相似文献   

18.
The phenomenon of ??switching?? of the domain walls generated by frustrations in a two-layer ferromagnet-antiferromagnet nanostructure has been studied using numerical simulation methods. This phenomenon manifests itself in the fact that, as the magnetic field increases, the ferromagnetic layer divided into nanodomains by domain walls perpendicular to the layer plane becomes single-domain, and the antiferromagnetic layer that is uniform in weak fields is divided into 180° domains by the domain walls perpendicular to the layer. The structures of these domain walls have been calculated in various magnetic fields.  相似文献   

19.
Changes in the magnetic moment of crystalline FeBO3 when an antiferromagnetic resonance is excited in it are studied. This done using a SQUID magnetometer in combination with a microwave spectrometer. At temperatures T>15 K a reduction in the total magnetic moment of the sample is observed when an antiferromagnetic resonance is excited in it. At liquid helium temperatures, an induced rise in the sample magnetic moment was observed. This type of magnetization of the sample can be explained qualitatively if it is assumed that under antiferromagnetic resonance excitation conditions, magnetoelastic modes with high wave numbers are excited along with magnons. Efficient excitation of magnetoelastic modes under antiferromagnetic resonance conditions is confirmed by the experimental observation of a size effect in thin, high quality single crystal slabs of FeBO3. Zh. éksp. Teor. Fiz. 115, 1107–1115 (March 1999)  相似文献   

20.
Epitaxial orthorhombic YMnO3 thin films, (0 0 1) oriented, have been grown by pulsed laser deposition on (0 0 1)SrTiO3 substrates. Their crystal structure and magnetic response have been studied in detail. Although bulk o-YMnO3 is antiferromagnetic, our magnetic measurements reveal intriguing thermal hysteresis between the zero-field-cooled and field-cooled curves below the onset of the antiferromagnetic ordering temperature, thus signaling a more complex magnetic structure with net ferromagnetic moments. We discuss on the possible origin of this net magnetization and we have found a correlation of the magnetic response with the strain state of the films. We propose that substrate-induced strain modifies the subtle competition of magnetic interactions and leads to a non-collinear magnetic state that can thus be tuned by strain engineering.  相似文献   

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