We propose a model of carrier-mediated ferromagnetism in semiconductors that accounts for the temperature dependence of the carriers. The model permits analysis of the thermodynamic stability of competing magnetic states, opening the door to the construction of magnetic phase diagrams. As an example we analyze the stability of a possible reentrant ferromagnetic semiconductor, in which increasing temperature leads to an increased carrier density, such that the enhanced exchange coupling between magnetic impurities results in the onset of ferromagnetism as temperature is raised.
Density functional studies of 26K superconducting LaFeAs(O,F) are reported. We find a low carrier density, high density of states, $N(E_F)$ and modest phonon frequencies relative to $T_c$. The high $N(E_F)$ leads to proximity to itinerant magnetism, with competing ferromagnetic and antiferromagnetic fluctuations and the balance between these controlled by doping level. Thus LaFeAs(O,F) is in a unique class of high $T_c$ superconductors: high $N(E_F)$ ionic metals near magnetism.
Since the discovery of room temperature ferromagnetism in (Ti,Co)O2, the mechanism has been under discussion for a decade. Particularly, the central concern has been whether or not the ferromagnetic exchange interaction is mediated by charge carriers like (Ga,Mn)As. Recent two studies on the control of ferromagnetism in anatase (Ti,Co)O2 at room temperature via electric field effect [Y. Yamada et al., Science 332, 1065 (2011)] and chemical doping [Y. Yamada et al., Appl. Phys. Lett. 99, 242502 (2011)] indicate a principal role of electrons in the carrier-mediated exchange interaction. In this …
InAs/AlAs$_{x}$Sb$_{1-x}$ quantum wells are investigated for their potential as hot carrier solar cells. Continuous wave power and temperature dependent photoluminescence indicate a transition in the dominant hot carrier relaxation process from conventional phonon-mediated carrier relaxation below 90 K to a regime where inhibited radiative recombination dominates the hot carrier relaxation at elevated temperatures. At temperatures below 90 K photoluminescence measurements are consistent with type-I quantum wells that exhibit hole localization associated with alloy/interface fluctuations. At el…
In the present work, we have prepared Mn-doped Ge using different annealing approaches after Mn ion implantation, and obtained samples with hole concentrations ranging from 10^18 to 2.1x10^20 cm^-3, the latter being the highest reported so far. Based on the magnetotransport properties of Mn doped Ge, we argue that the hole concentration is a decisive parameter in establishing carrier-mediated ferromagnetism in magnetic Ge.
We analyze the origin of ferromagnetism as a result of carrier mediation in diluted magnetic oxide semiconductors in the light of the experimental evidence reported in the literature. We propose that a combination of percolation of magnetic polarons at lower temperature and Ruderman-Kittel-Kasuya-Yosida ferromagnetism at higher temperature may be the reason for the very high critical temperatures measured (up to ~700 K).
We explore spin dynamics in Cu(1,3-bdc), a quasi-2D topological magnon insulator. The results show that the thermal evolution of Landé $g$-factor ($g$) is anisotropic: $g_\textrm{in-plane}$ reduces while $g_\textrm{out-plane}$ increases with increasing temperature $T$. Moreover, the anisotropy of the $g$-factor ($Δg$) and the anisotropy of saturation magnetization ($ΔM_\textrm{s}$) are correlated below 4 K, but they diverge above 4 K. We show that the electronic orbital moment contributes to the $g$ anisotropy at lower $T$, while the topological orbital moment induced by thermally excited spin…
One of the keys to the realization of Quantum Anomalous Hall effect (QAHE) is long range ferromagnetism, which is only experimentally realized in Cr or V doped (Bi,Sb)2Te3 system. Both elements are 3d transition metals and 4d transition metals are found to be ineffective to produce long range ferromagnetism in Bi2Se3. Still, whether long range ferromagnetism can be realized by magnetic doping of 4d elements is an open question. Based on density functional theory calculations, we predict that long range ferromagnetism can be realized in Mo doped Bi2Te3 and Sb2Te3, which are semiconducting. The …
We report the observation of carrier mediated decrease in the stiffness of crystalline (c)-Si(100) under nanoindentation. The apparent elastic modulii of heavily dopes (1E21 cm-3) p- and n-type c-Si are observed to be lower by 5.-7.5 percent that the estimated value for intrinsic (1E14 cm-3) c-Si. The deviation observed with respect to elastic modulus remarkably matches with the estimated value while considering the electronic elastic strain effect on carrier concentration as an influence of negative pressure coefficient of band gap for Si. The value is predominantly higher than the reported v…
We report the fabrication of Ge:Mn ferromagnetic semiconductors by Mn-ion implantation into Ge followed by pulsed laser annealing. Benefiting from the short time annealing, the hole concentration in Mn-implanted Ge has been increased by two orders of magnitude from 10$^{18}$ to over 10$^{20}$ cm$^{-3}$. Likely due to the high hole concentration, we observe that the longitudinal and Hall resistances exhibit the same hysteresis as the magnetization, which is usually considered as a sign of carrier-mediated ferromagnetism.
The effects of $n$-type carrier doping by Li intercalation on magnetism in undoped and Co-doped anatase TiO$_2$ are investigated. We have found that doped $n$-type carriers in TiO$_2$ are localized mainly at Ti sites near the intercalated Li. With increasing the intercalation, local spins are realized at Ti. In the case of Co-doped TiO$_2$, most of the added $n$-type carriers fill the Co 3$d$ bands and the rest are localized at Ti. Therefore, Co magnetic moment vanishes by Li intercalation to have a nonmagnetic ground state.
We study the enhancement of the magnetic transition temperature $T_c$ due to incident light in ferromagnetic semiconductors such as EuS. The photoexcited carriers mediate an extra ferromagnetic interaction due to the coupling with the localized magnetic moments. The Hamiltonian consists of a Heisenberg model for the localized moments and an interaction term between the photoexcited carriers and the localized moments. The model predicts a small enhancement of the transition temperature in semi-quantitative agreement with the experiments.
Electronic properties of the single crystal of GdV6Sn6, where non-magnetic V-kagome layers are separated by magnetic Gd-triangular lattice, are investigated. GdV6Sn6 exhibits unique magnetotransport properties at low-temperature such as non-linear Hall resistivity and increase of resistance R in magnetic field H as R ~ H^0.75 up to 56 T with Shubnikov-De Haas oscillations. Investigation of the non-magnetic analogue YV6Sn6 and the first principles calculations reveal these properties are relevant to the bands arising from the V-kagome layer. A magnetic transition at 5 K in GdV6Sn6 modifies the …
The presence of localized spins exerts a strong influence on quantum localization in doped semiconductors. At the same time carrier-mediated interactions between the localized spins are modified or even halted by carriers' localization. The interplay of these effects is discussed for II-VI and III-V diluted magnetic semiconductors. This insight is exploited to interpret the complex dependence of resistance on temperature, magnetic field, and concentration of valence-band holes in (Ga,Mn)As. In particular, high field negative magnetoresistance results from the orbital weak localization effect. …
Free electrons or holes can mediate the nonradiative recombination of excitons in carbon nanotubes. Kinematic constraints arising from the quasi one-dimensional nature of excitons and charge carriers lead to a thermal activation barrier for the process. However, a model calculation suggests that the rate for recombination mediated by a free electron is the same order of magnitude as that of two-exciton recombination. Small amounts of doping may contribute to the short exciton lifetimes and low quantum yields observed in carbon nanotubes.
We show that the presence of free carriers in a substance can generate the multiferroic behavior. Namely, if the substance has mixed-valence ions, which can supply free carriers and have electric dipole and spin moments, all three types of long-range order (ferromagnetic, ferroelectric and magnetoelectric (ME)) can occur at low temperature. The physical origin of the effect is that charge carriers can mediate the multiferroic behavior via spin - spin (RKKY), dipole-dipole and dipole - spin interactions. Our estimate of the interaction magnitude shows that there exist an optimal carrier concent…
While tremendous success has been achieved to date in creating both single phase and composite magnetoelectric materials, the quintessential electric-field control of magnetism remains elusive. In this work, we demonstrate a linear magnetoelectric effect which arises from a novel carrier-mediated mechanism, and is a universal feature of the interface between a dielectric and a spin-polarized metal. Using first-principles density functional calculations, we illustrate this effect at the SrRuO$_3$/SrTiO$_3$ interface and describe its origin. To formally quantify the magnetic response of such an …
Dirac materials exhibit intriguing low-energy carrier dynamics that offer a fertile ground for novel physics discovery. Of particular interest is the interplay of Dirac carriers with other quantum phenomena, such as magnetism. Here we report on a two-magnon Raman scattering study of AMnBi2 (A=Ca, Sr), a prototypical magnetic Dirac system comprising alternating Dirac-carrier and magnetic layers. We present the first accurate determination of the exchange energies in these compounds and, by comparison to the reference compound BaMn2Bi2, we show that the Dirac-carrier layers in AMnBi2 significant…
The mechanism behind ferromagnetic exchange interaction in GdN is not well understood. It has been argued that it can be due to fourth order cross process of \textit{d-f} mixing and \textit{d-f} exchange. An alternative explanation suggests an anti- ferromagnetic interaction between Gd \textit{d} and N \textit{p} induced moments on the rock salt structure which aligns the nearest neighbor Gd \textit{f} moments ferromagnetically through the \textit{d-f} exchange. In this paper we present results of Curie temperature in GdN as a function of carrier density calculated within our multiband modifie…
Highly p-type GaAs:C was ion-implanted with Mn at differing doses to produce Mn concentrations in the 1 - 5 at.% range. In comparison to LT-GaAs and n+GaAs:Si samples implanted under the same conditions, transport and magnetic properties show marked differences. Transport measurements show anomalies, consistent with observed magnetic properties and with epi- LT-(Ga,Mn)As, as well as the extraordinary Hall Effect up to the observed magnetic ordering temperature (T_C). Mn ion-implanted p+GaAs:C with as-grown carrier concentrations > 10^20 cm^-3 show remanent magnetization up to 280 K.
First-principles calculations to study the electronic and magnetic properties of bulk, oxygen-deficient SrTiO$_3$ (STO) under different doping conditions and densities have been conducted. The appearance of magnetism in oxygen-deficient STO is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. We find that while an isolated vacancy behaves as a non-magnetic double donor, manipulation of the doping conditions allows the stability of a single donor state, with emergent local moments coupled ferromag…
We use two recently proposed methods to calculate exactly the spectrum of two spin-${1\over 2}$ charge carriers moving in a ferromagnetic background, at zero temperature, for three types of models. By comparing the low-energy states in both the one-carrier and the two-carrier sectors, we analyze whether complex models with multiple sublattices can be accurately described by simpler Hamiltonians, such as one-band models. We find that while this is possible in the one-particle sector, the magnon-mediated interactions which are key to properly describe the two-carrier states of the complex model …
Emergence of half-semiconductor behavior and tunable magnetism via carrier doping in Janus VXSe (X=Cl, Br, I) monolayers
Southwest University（西南大学）；Hanhong College, Southwest University（汉弘学院，西南大学）；AECC Hunan Aviation Powerplant Research Institute（中国航发湖南航空发动机研究所）；Chengdu University of Technology（成都理工大学）；Leshan Normal University（乐山师范学院）；Shanghai Jiao Tong University（上海交通大学）
We explore possible ways to manipulate the intrinsic edge magnetism in hexagonal graphene nanoflake with zigzag edges, using density functional theory supplemented with on-site Coulomb interaction. The effect of carrier doping, chemical modification at the edge, and finite temperature on the edge magnetism has been studied. The magnetic phase diagram with varied carrier doping, and on-site Coulomb interaction is found to be complex. In addition to the intrinsic antiferromag- netic solution, as predicted for charge neutral hexagonal nanoflake, fully polarized ferromagnetic, and mixed phase solu…
We present a comprehensive theoretical study of the static spin response in HgTe quantum wells, revealing distinctive behavior for the topologically nontrivial inverted structure. Most strikingly, the q=0 (long-wave-length) spin susceptibility of the undoped topological-insulator system is constant and equal to the value found for the gapless Dirac-like structure, whereas the same quantity shows the typical decrease with increasing band gap in the normal-insulator regime. We discuss ramifications for the ordering of localized magnetic moments present in the quantum well, both in the insulating…
We report femtosecond time-resolved reflectivity measurements of coherent phonons in tellurium performed over a wide range of temperatures (3K to 296K) and pump laser intensities. A totally symmetric A$_{1}$ coherent phonon at 3.6 THz responsible for the oscillations in the reflectivity data is observed to be strongly positively chirped (i.e, phonon time period decreases at longer pump-probe delay times) with increasing photoexcited carrier density, more so at lower temperatures. We show for the first time that the temperature dependence of the coherent phonon frequency is anomalous (i.e, incr…
The carrier dynamics in bulk Silicon, a paradigmatic indirect gap semiconductor, is studied by using the Baym-Kadanoff equations. Both the electron--electron(e-e) and electron--phonon(e-p) self--energies are calculated fully ab-initio by using a semi-static GW approximation in the e-e case and a Fan self-energy in the e-p case. By using the generalized Baym-Kadanoff ansatz the two-time evolution is replaced by the only dynamics on the macroscopic time axis. The enormous numerical difficulties connected with a real-time simulation of realistic systems is overcame by using a completed collision …
We use neutron reflectometry to investigate the interlayer exchange coupling between Ga$_{0.97}$Mn$_{0.03}$As ferromagnetic semiconductor layers separated by non-magnetic Be-doped GaAs spacers. Polarized neutron reflectivity measured below the Curie temperature of Ga$_{0.97}$Mn$_{0.03}$As reveals a characteristic splitting at the wave vector corresponding to twice the multilayer period, indicating that the coupling between the ferromagnetic layers are antiferromagnetic (AFM). When the applied field is increased to above the saturation field, this AFM coupling is suppressed. This behavior is no…
The excited holes occupying the valence band tail states in amorphous oxide semiconductors are found to induce formation of meta-stable O$_2^{2-}$ peroxide defects. The valence band tail states are at least partly characterized by the O-O ppσ* molecular orbital, and the localized-hole-mediated lattice instability results in the formation of the peroxide defects. Along with the O-O bond formation, the ppσ* state is heightened up into the conduction bands, and two electrons are accordingly doped in the electronic ground state. The energy barrier from the O$_2^{2-}$ peroxide state to the normal d…
In a semiconductor heterostructure with type II energy band alignment, the spatial separation between electrons and holes slows down their radiative recombination. With increasing excitation intensity, Auger recombination quickly becomes the dominate recombination channel, and it produces carrier ejection from the quantum well. Here, we show that in Si/SiGe three-dimensional nanostructures, this efficient process facilitates the formation of an electron-hole plasma (EHP) and/or electron-hole droplets (EHDs) in thin Si barriers separating SiGe clusters. In contrast to conventional, strongly tem…
We find, through first-principles calculations, that hole doping induces a ferromagnetic phase transition in monolayer GaSe. Upon increasing hole density, the average spin magnetic moment per carrier increases and reaches a plateau near 1.0 $μ_{\rm{B}}$/carrier in a range of $3\times 10^{13}$/cm$^{2}$-$1\times 10^{14}$/cm$^{2}$ with the system in a half-metal state before the moment starts to descend abruptly. The predicted magnetism originates from an exchange splitting of electronic states at the top of the valence band where the density of states exhibits a sharp van Hove singularity in thi…
We propose two new methods to calculate exactly the spectrum of two spin-${1\over 2}$ charge carriers moving in a ferromagnetic background, at zero temperature. We find that if the spins are located on a different sublattice than that on which the fermions move, magnon-mediated effective interactions are very strong and can bind the fermions into low-energy bipolarons with triplet character. This never happens in models where spins and charge carriers share the same lattice, whether they are in the same band or in different bands. This proves that effective one-lattice models do not describe c…
We discuss a new class of phenomena based on strong interaction between magnetic superstructures and vortices in superconductors in combined heterogeneous structures. An inhomogeneous magnetization can pin vortices or create them spontaneously changing drastically properties of the superconductor. On the other hand, the interaction between magnetic moments mediated by vortices can result in specific types of magnetic ordering. The same interaction can create coupled magnetic-superconducting defects. We discuss possible experimental observation of magnetism controlled vortex matter in supercond…
We have investigated magnetic interactions between transition metal ions in bismuthene topological insulator with protected edge states. We find that these topological states have a crucial role on the magnetic interactions in 2D topological insulators. Using first-principles and model Hamiltonian we make a comparative study of transition metal doped bulk and nanoribbon bismuthene. While direct overlap between the transition metal prevails in gapped bulk bismuthene, at the borders of nanoribbons a long-range magnetism is present. The exchange interactions are well described by a RKKY-like Hami…
RuGe, a diamagnetic small-band gap semiconductor, and CoGe, a nonmagnetic semimetal, are both isostructural to the Kondo insulator FeSi and the skyrmion lattice host MnSi. Here, we have explored the magnetic and transport properties of Co-doped RuGe: Ru$_{1-x}$Co$_x$Ge. For small values of $x$, a magnetic ground state emerges with $T_{c}\approx$ 5 $-$ 9 K, which is accompanied by a moderate decrease in electrical resistivity and a Seebeck coefficient that indicates electron-like charge carriers. The magnetization, magnetoresistance, and the specific heat capacity all resemble that of Fe$_{1-x}…
Realizing magnetism in graphene/carbon nanostructures is a decade-long challenge. The magnetic edge state and half metallicity in zigzag graphene nanoribbons are particularly promising [Y.-W. Son, et al., Nature 444, 347 (2006)]. However, its experimental realization has been hindered by the stringent requirement of the mono-hydrogenated zigzag edge. Using first-principle calculations, we predict that free-carrier doping can overcome this challenge and realize ferromagnetism and half-metallicity in narrow graphene nanoribbons of general types of edge structures. This magnetism exists within th…
Despite the recent success in the realization of the quantum anomalous Hall effect, the underlying physical mechanism of the long range Ferromagnetism is still unclear. Based on our density functional theory calculations, we discovered an intriguing long-range ferromagnetic order in Cr-doped, carrier-free Bi2Te3, with the separation between dopants more than 8 Å. We found that this magnetic coupling is facilitated by an anti-bonding state originated from the lone pair of a Te 5p state and a Bi 6s state, despite this anti-bonding state lies below the valence band maximum. Such a state serves as…
Ion implantation of Mn ions into hole-doped GaP has been used to induce ferromagnetic behavior above room temperature for optimized Mn concentrations near 3 at.%. The magnetism is suppressed when the Mn dose is increased or decreased away from the 3 at.% value, or when n-type GaP substrates are used. At low temperatures the saturated moment is on the order of one Bohr magneton, and the spin wave stiffness inferred from the Bloch-law T^3/2 dependence of the magnetization provides an estimate Tc = 385K of the Curie temperature that exceeds the experimental value, Tc = 270K. The presence of ferro…
The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of defects in the materials, which are not necessarily detrimental for certain applications. For instance, defects can lead to an enhanced photoconduction, a complicated process involving charge generation and recombination in the time domain and carrier transport in the spatial domain. Here, we report the simultaneous spatial and temporal photoconductivity imaging in two types of WS2 monolayers by laser-illuminated microwave impedance microscopy. The diffusion length and…
In heterostructures of LaAlO3 (LAO) and SrTiO3 (STO), two nonmagnetic insulators, various forms of magnetism have been observed [1-7], which may [8, 9] or may not [10] arise from interface charge carriers that migrate from the LAO to the interface in an electronic reconstruction [11]. We image the magnetic landscape [5] in a series of n-type samples of varying LAO thickness. We find ferromagnetic patches that appear only above a critical thickness, similar to that for conductivity [12]. Consequently we conclude that an interface reconstruction is necessary for the formation of magnetism. We ob…
We study theoretically the RKKY interaction between magnetic impurities on the surface of three-dimensional topological insulators, mediated by the helical Dirac electrons. Exact analytical expression shows that the RKKY interaction consists of the Heisenberg-like, Ising-like and DM-like terms. It provides us a new way to control surface magnetism electrically. The gap opened by doped magnetic ions can lead to a short-range Bloembergen-Rowland interaction. The competition among the Heisenberg, Ising and DM terms leads to rich spin configurations and anomalous Hall effect on different lattices.
Recent experiments [1] suggest that the ferromagnetism (FM) in GaAs: Mn is determined by the impurity band rather than holes in the valence band. We discuss here the physical mechanism of FM mediated by the carriers in impurity band, where the Mn d-level play a crucial role. The theory is based on the first principle approach.
We demonstrate that room-temperature ferromagnetism in epitaxial Co-doped TiO2 anatase is driven by electron-mediated exchange interaction, and not by metallic Co clusters. Co(II) substitutes for Ti(VI) in the lattice and produces oxygen vacancies that do not contribute carriers. Free electrons originate with oxygen vacancies resulting from an oxygen deficiency during growth.
Nitrogen-Vacancy-Mediated Magnetism in Sputtered GdN Thin Films
Indian Institute of Science（印度科学研究所）；Jawaharlal Nehru Center for Advanced Scientific Research（贾瓦哈拉尔·尼赫鲁高级科学研究中心）；Indian Institute of Technology Madras（马德拉斯印度理工学院）；IISER Thiruvananthapuram（特凡纳普拉姆印度科学教育研究院）；BITS Pilani K. K. Birla Goa Campus（比拉工业与科学研究所皮拉尼校区K.K.比尔拉果阿分校）
Fermi level dependence of magnetism and magnetotransport in the magnetic topological insulators Bi$_{2}$Te$_{3}$ and BiSbTe$_{3}$ containing self-organized MnBi$_{2}$Te$_{4}$ septuple layers
In order to determine the role of non-thermal transport of hot carriers which is decisive for the dissipation of energy in condensed matter we performed time-resolved broadband femtosecond transient reflectivity measurements on $7-197 \mathrm{nm}$ thick Bi(111) films epitaxially grown on Si(111). We monitored the behavior of the Fourier amplitude and the central frequency of the coherent $A_\mathrm{1g}$ phonon mode as function of the incident fluence, film thickness, and probe wavelength in the range of $580 -700 \mathrm{nm}$. The frequency redshift that follows photoexcitation was used as a r…
Zirconium pentatelluride ZrTe$_5$, a fascinating topological material platform, hosts exotic chiral fermions in its highly anisotropic three-dimensional Dirac band and holds great promise advancing the next-generation information technology. However, the origin underlying its anomalous resistivity peak has been under debate for decades. Here we provide transport evidence substantiating the anomaly to be a direct manifestation of a Lifshitz transition in the Dirac band with an ultrahigh carrier mobility exceeding 3$\times$10$^5$ cm$^2$ V$^{-1}$ s$^{-1}$. We demonstrate that the Lifshitz transit…
Ion irradiation of semiconductors is a well understood method to tune the carrier concentration in a controlled manner. We show that the ferromagnetism in GaMnAs films, known to be hole-mediated, can be modified by He ion irradiation. The coercivity can be increased by more than three times. The magnetization, Curie temperature and the saturation field along the out-of-plane hard axis all decrease as the fluence increases. The electrical and structural characterization of the irradiated GaMnAs layers indicates that the controlled tailoring of magnetism results from a compensation of holes by g…
Carrier-tunable RKKY magnetism in a crystalline magnet
the University of Tokyo（东京大学）；University of St Andrews（圣安德鲁斯大学）；RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所物质结构科学研究中心）；Institute of Industrial Science, the University of Tokyo（东京大学工业技术科学研究所）；Graduate School of Informatics and Engineering, The University of Electro-Communications（电气通信大学信息工程研究生院）；The Institute for Solid State Physics, University of Tokyo（东京大学固体物理研究所）；Institute of Materials Structure Science, High Energy Accelerator Research Organization（高能加速器研究机构物质结构科学研究所）
We have studied the properties of relatively thick (about 120 nm) magnetic composite films grown by pulsed laser deposition method using (GaSb)$_{0.59}$(MnSb)$_{0.41}$ eutectic compound as a target for sputtering. For the studied films we have observed ferromagnetism and anomalous Hall effect above the room temperature, it manifests the presence of spin-polarized carriers. Electron microscopy, atomic and magnetic force microscopy results suggests that films under study have homogenous columnar structure in the bulk while MnSb inclusions accumulate near it's surface. This is in good agreement w…
We have experimentally tested the hypothesis of free charge carrier mediated spin-transport in the small molecule organic semiconductor Alq3 at room temperature. A spin current was pumped into this material by pulsed ferromagnetic resonance of an adjacent NiFe layer, while a charge current resulting from this spin current via the inverse spin-Hall effect (ISHE) was detected in a Pt layer adjacent on the other side of the Alq3 layer, confirming a pure spin current through the Alq3 layer. Charge carrier spin states in Alq3, were then randomized by simultaneous application of electron paramagneti…
We study the non-collinear exchange coupling across a trilayer magnetic junction consisting of two ferromagnets separated by a thin dilute magnetic semiconductor containing itinerant carriers with finite spin relaxation. It is remarkable that, by increasing the spin relaxation, the critical temperature is substantially enhanced and the shape of the magnetization curve becomes more mean-field like. We attribute these interesting changes to the broken time-reversal symmetry which suppresses the oscillatory Ruderman-Kittel-Kasuya-Yosida interaction. Our argument is further strengthened by the eme…
We study the coexistence of strain- and charge-mediated magnetoelectric coupling in a cobalt (0-7 nm) wedge on ferroelectric [Pb(Mg$_{1/3}$/Nb$_{2/3}$)O$_{3}$]$_{0.68}$-[PbTiO$_{3}$]$_{0.32}$ (011) using surface-sensitive x-ray magnetic circular dichroism spectroscopy at the Co L$_{3,2}$ edges. Three distinct electric field driven remanent magnetization states can be set in the Co film at room temperature. Ab-initio density functional theory calculations unravel the relative contributions of both strain and charge to the observed magnetic anisotropy changes illustrating magnetoelectro-elastic …
