We report density functional calculations addressing the electronic structure and magnetic properties of delafossite PdCrO2. We find substantial magnetic interactions in the c-axis direction as well as beyond first nearest neighbors in-plane, so that PdCrO2 is a 3D frustrated antiferromagnet. We also find substantial coupling between the Cr moments and the Pd derived conduction electrons.
We find evidence that superconductivity intrudes into the paramagnetic-to-magnetic transition of the Kondo lattice model if magnetic frustration is added. Specifically, we study by variational method the model on a square lattice in the presence of both nearest- ($t$) and next-nearest-neighbor ($t^\prime$) hopping of the conduction electrons. We find that when $t^\prime/t$ is finite a $d$-wave superconducting dome emerges between the magnetic and paramagnetic metal phases and close to the compensated regime, i.e., the number of conduction electrons equal to the number of localized spin-1/2 mom…
Highly energetic magnetic fluctuations, discovered in high-temperature superconductors (HTSC) by inelastic neutron scattering (INS), are now widely believed to be vital for the superconductivity. In two competing scenarios, they either originate from local atomic spins, or are a property of cooperative spin-density-wave (SDW) behavior of conduction electrons. Both assume clear partition into localized electrons, giving rise to local spins, and itinerant ones, occupying well-defined, rigid conduction bands. Here, by performing an INS study of spin dynamics in iron telluride, a parent material o…
Effect of level statistics on local electronic states and local magnetism in nanoscale metallic grains with transition-metal impurity in the ballistic regime is studied. It is shown that the mean occupation of local electron and the local magnetic moment in nanoscale metallic grains with odd conduction electrons are larger than those with even conduction electrons. The effect of even-odd parity on the condition for the occurrence of local magnetic moment is also discussed, it is found that the critical value $ρ_{d}(0)U_{c}$ for the formation of local moment in nanoscale metallic grains is much…
We have compared the magnetic, transport, galvanomagnetic and specific heat properties of CeNiC$_2$, PrNiC$_2$ and NdNiC$_2$ to study the interplay between charge density waves and magnetism in these compounds. The negative magnetoresistance in NdNiC$_2$ is discussed in terms of the partial destruction of charge density waves and an irreversible phase transition stabilized by the field induced ferromagnetic transformation is reported. For PrNiC$_2$ we demonstrate that the magnetic field initially weakens the CDW state, due to the Zeeman splitting of conduction bands. However, the Fermi surface…
We present a theory of magnetic and magneto-transport phenomena at LaAlO$_3$/SrTiO$_3$ interfaces, which as a central ingredient includes coupling between the conduction bands and local magnetic moments originating from charge traps at the interface. Tuning the itinerant electron density in the model drives transitions between a heavy Fermi liquid phase with screened moments and various magnetic states. The dependence of the magnetic phenomena on the electron density or gate voltage stems from competing magnetic interactions between the local moments and the different conduction bands. At low …
Kondo-based semimetals and semiconductors are of extensive current interest as a viable platform for strongly correlated states. It is thus important to understand the routes towards such dilute-carrier correlated states. One established pathway is through Kondo effect in metallic non-magnetic analogues. Here we advance a new mechanism, through which Kondo-based semimetals develop out of conduction electrons with a low carrier-density in the presence of an even number of rare-earth sites. We demonstrate this effect by studying the Kondo material Yb3Ir4Ge13 along with its closed-f-shell counter…
The Periodic Anderson Model (PAM) is widely studied to understand strong correlation physics and especially the competition of antiferromagnetism and singlet formation. Quantum Monte Carlo (QMC) studies have focused both on issues such as the nature of screening and locating the quantum critical point (QCP) at zero temperature and also on possible experimental connections to phenomena ranging from the Cerium volume collapse to the relation of the magnetic susceptibility and Knight shift in heavy fermions. In this paper we extend QMC work to lattices in which the conduction electron sites can h…
By calculating the spectral density of states in the ferromagnetic (FM) ground state and in the high temperature paramagnetic (PM) phase we provide the first concise study of finite temperature effects on the electronic structure of the bulk and the surface of gadolinium metal. The variation of calculated spectral properties of the Fermi surface and the density of states in the bulk and at the surface are in good agreement with recent photoemission experiments performed in both ferromagnetic and paramagnetic phases. In the paramagnetic state we find vanishing spin splitting of the conduction b…
We study the low-temperature behavior of a magnetic impurity which is weakly coupled to correlated conduction electrons. To account for conduction electron interactions a diagrammatic approach in the frame of the 1/N expansion is developed. The method allows us to study various consequences of the conduction electron correlations for the ground state and the low-energy excitations. We analyse the characteristic energy scale in the limit of weak conduction electron interactions. Results are reported for static properties (impurity valence, charge susceptibility, magnetic susceptibility, and spe…
The large-degeneracy expansion for dilute magnetic alloys is extended to account for conduction electrons interactions. Particular attention is paid to the renormalization of the hybridization vertex which affects the low-energy excitations. As a first example, we calculate the enhanced characteristic energy $k_BT_0$ in the limit of weakly correlated conduction electrons. The metallic regime with strongly correlated electrons is discussed.
The Hubbard model in the Heisenberg limit is studied by Kondo-lattice theory. The Kondo temperature T_K or k_BT_K, which is an energy scale of low-energy local quantum spin fluctuations, is enhanced by the resonating valence bond (RVB) mechanism, so that T_K\simeq T_MF/(2D), where T_MF is the Neel temperature in the mean-field approximation of the corresponding Heisenberg model and D is the spatial dimensionality. Electrons certainly behave as localized spins at T\gg T_K, but they are still itinerant at T\ll T_K unless an antiferromagnetic complete gap opens. When the Neel temperature T_N is s…
A novel approach to electronic correlations and magnetism of crystals based on realistic electronic structure calculations is reviewed. In its simplest form it is a combination of the ``local density approximation'' (LDA) and the dynamical mean field theory (DMFT) approaches. Using numerically exact QMC solution to the effective DMFT multi-orbital quantum-impurity problem, a successful description of electronic structure and finite temperature magnetism of transition metals has been achieved. We discuss a simplified perturbation LDA+DMFT scheme which combines the T-matrix and fluctuation-excha…
We report the normal-state transport and magnetic properties of a pressure-induced superconductor CeTe$_{1.82}$. We found that the applied pressure is required to increase the Kondo temperature scale ($T^*_{\rm K} \sim$ 170 K), associated with the two-dimensional motion of the carriers confined within the Te plane. Both the short-range ferromagnetic ordering temperature ($T_{\rm SRF} \sim$ 6 K) and the long-range antiferromagnetic transition temperature ($T_{\rm N} \sim$ 4.3 K) are slightly increased with pressure. We suggest that the application of pressure enhances a coupling between the 4$f…
The desire to maximize the sensitivity of read/write heads and thus the information density of magnetic storage devices has produced an intense interest in the magnetoresistance (MR) of magnetic materials. Recent discoveries include "colossal" MR of the manganites1-4 and the enhanced MR of low carrier density ferromagnets4-6. In the low carrier density systems investigated to date as well as the manganites, a key feature is that the electrical conduction is due to a different set of electrons than the localized electrons responsible for the magnetism. Here we propose a mechanism for ferromagne…
We report a study of electronic transport in van der Waals heterostructures composed of flakes of the antiferromagnetic Mott insulator a-RuCl_3 placed on top of monolayer graphene Hall bars. While the zero-field transport shows a strong resemblance to that of isolated graphene, we find a consistently $p$-type Hall effect suggestive of multiband conduction, along with a non-monotonic and gate-voltage-dependent excursion of the resistivity at low temperatures that is reminiscent of transport in the presence of a magnetic phase transition. We interpret these data as evidence for charge transfer f…
We have calculated the discrete low-energy electronic structure in LaMnO3 originating from the atomic-like states of the strongly correlated 3d4 electronic system occurring in the Mn3+ ion. We take into account very strong intra-atomic correlations, crystal field interactions and the intra-atomic spin-orbit coupling. We calculated magnetic and paramagnetic state of LaMnO3 within the consistent description given by Quantum Atomistic Solid State Theory (QUASST). Our studies indicate that the intra-atomic spin-orbit coupling and the orbital magnetism are indispensable for the physically adequate …
Spin-spin correlation function response in the low electronic density regime and externally applied electric field is evaluated for 2D metallic crystals under Rashba-type coupling, fixed number of particles and two-fold energy band structure. Intrinsic Zeeman-like effect on electron spin polarization, density of states, Fermi surface topology and transverse magnetic susceptibility are analyzed in the zero temperature limit. A possible magnetic state for Dirac electrons depending on the zero field band gap magnitude under this conditions is found.
Photoirradiation effects in correlated electrons coupled with localized spins are studied based on the extended double-exchange model. In particular, we examine melting of an antiferromagnetic (AFM) charge order insulating state by varying the light intensity. When intense light is irradiated, the AFM insulating characteristics are strengthened, rather than change into the ferromagnetic metallic characteristic, which are expected from the conventional double exchange interaction when carriers are introduced by weak light irradiation or chemical doping. This provides a new principle for optical…
We have calculated the energies of the phase-separated states for degenerate antiferromagnetic semiconductors including the possibility of the existence of conduction electrons in the antiferromagnetic part of the phase-separated states. It is demonstrated that, at T=0, the minimum energy corresponds to a droplet phase with absence of electrons in the antiferromagnetic part.
The electronic structure and magnetism of Sr$_2$CeIrO$_6$, an Ir-based double perovskite system has been investigated using first-principles calculations. We found that a strong spin-orbit coupling dictate the electronic and magnetic properties of this system. A small value of $U$ along with SOC could open up a gap at the Fermi level, offering the possibility of novel J$_{eff}$ = 1/2 Mott quantum state. Our calculations reveal that the magnetic ground state is antiferromagnetic in agreement with the magnetization data and provide the value of spin and orbital moment for this system which is in…
The spinless Falicov-Kimball model is one of the simplest models of many-body physics. While the conduction-electron density of states is temperature independent in the normal state, the f-electron density of states is strongly temperature dependent---it has an orthogonality catastrophe singularity in the metallic phase and is gapped in the insulating phase. The question we address here is whether the spectral gap is the same for both electron species as T->0. We find strong evidence to indicate that the answer is affirmative.
Magnetic topological materials are a class of compounds with the underlying interplay of nontrivial band topology and magnetic spin configuration. Extensive interests have been aroused due to their application potential involved with an array of exotic quantum states. With angle-resolved photoemission spectroscopy and first-principles calculations, here we study the electronic properties of two magnetic Weyl semimetal candidates PrAlSi and SmAlSi. Though the two compounds harbor distinct magnetic ground states (ferromagnetic and antiferromagnetic for PrAlSi and SmAlSi, respectively) and 4$f$ s…
A spin-1/2 magnetic impurity coupled to a one-dimensional correlated electron system have been studied by applying the density renormalization group method. The Kondo temperature is substantially enhanced by strong repulsive interactions in the chain, but changes non-monotonically in the case of electron attraction. The magnetization of the impurity at zero- temperature shows local Fermi liquid behavior.
We investigate magnetic polarons in two-dimensional strongly correlated electron systems, where conduction electrons interact with antiferromagnetically interacting localized spins. Starting from a basic model, we derive a simplified model with the help of spin Green's function and a perturbation analysis. A strong coupling analysis is applied to the model, where the sum of the scattering wave vectors is approximated to be $(π,π)$ or zero, using the equation of motion for the conduction electron Green's function, and we discuss the pseudogap like behavior associated with the suppression of the…
The Shubnikov-de Haas effect is used to explore the conduction band edge of high mobility SrTiO3 films doped with La. The results largely confirm the earlier measurements by Uwe et al. [Jap. J. Appl. Phys. 24, Suppl. 24-2, 335 (1985)]. The band edge dispersion differs significantly from the predictions of ab initio electronic structure theory.
In the analysis of the heavy electron systems, theoretical models with c-f hybridization gap are often used. We point out that such a gap does not exist and the simple picture with the hybridization gap is misleading in the metallic systems, and present a correct picture by explicitly constructing an effective band model of YbAl_3. Hamiltonian consists of a nearly free electron model for conduction bands which hybridize with localized f-electrons, and includes only a few parameters. Density of states, Sommerfeld coefficient, f-electron number and optical conductivity are calculated and compare…
A dynamical generalisation of the nonlocal coherent-potential approximation is derived based upon the functional integral approach to the interacting electron problem. The free energy is proven to be variational with respect to the self-energy provided a self-consistency condition on a cluster of sites is satisfied. In the present work, calculations are performed within the static approximation and the effect of the nonlocal physics on the formation of the local moment state in a simple model is investigated. The results reveal the importance of the dynamical correlations.
Structural, magnetic, and dielectric properties of Sm$_2$CoMnO$_6$ have been studied. X-ray diffraction and Rietveld analysis show that the sample crystallizes in the monoclinic structure with \textit{P2$_1$/n} space group. Magnetic study shows that the sample undergoes a paramagnetic to ferromagnetic phase transition around $T_c$ $\sim$148 K and a low-temperature ordering of Sm$^{3+}$ moments. Temperature-dependent Raman study shows spin-phonon coupling present in this material. Dielectric response of Sm$_2$CoMnO$_6$ shows strong frequency dependence with large dispersion and large dielectric…
Kagome magnets are expected to feature emergent properties due to the interplays among geometry, magnetism, electronic correlation, and band topology. The magnetism and topological electronic states can be tuned via the rare earth engineering in RV6Sn6 kagome metals, where R is a rare earth element. Herein, we present the synthesis and characterization of SmV6Sn6, a metal with two-dimensional kagome nets of vanadium and frustrated triangular Sm lattice. Partial of the Sm atoms are shifted from the normal R positions by c/2 along the c axis. Magnetic measurements reveal obvious anisotropy, wher…
We study the dynamical magnetic susceptibility of a strongly correlated electronic system in the presence of a time-dependent hopping field, deriving a generalized Bethe-Salpeter equation which is valid also out of equilibrium. Focusing on the single-orbital Hubbard model within the time-dependent Hartree-Fock approximation, we solve the equation in the non-equilibrium adiabatic regime, obtaining a closed expression for the transverse magnetic susceptibility. From this, we provide a rigorous definition of non-equilibrium (time-dependent) magnon frequencies and exchange parameters, expressed in…
The spinless resonant level model is studied when it is coupled by hopping to one of the arbitrary number of conduction electron channels. The Coulomb interaction acts between the electron on the impurity and in the different channels. In case of repulsive or attractive interaction the conduction electrons are pushed away or attracted to ease or hinder the hopping by creating unoccupied or occupied states, respectively. In the screening of the hopping orthogonality catastrophe plays an important role. In equilibrium the weak and strong coupling limit the renormalizations are treated by perturb…
Here, we report an investigation of structural, magnetic and electronic properties in Y-doped layered iridate (Sr$_{1-x}$Y$_x$)$_2$IrO$_4$ ($x$ $\leq$ 0.1). The parent Sr$_2$IrO$_4$ is a well-studied spin-orbit coupling (SOC) induced insulator with an antiferromagnetic ground state. The Y-doping here equivalently acts for electron doping without altering the vital parameters such as, SOC and electron correlation. Experimental results show a minute change in structural parameters and an equivalent charge conversion from Ir$^{4+}$ to Ir$^{3+}$. Unlike similarly other electron-doped system, the l…
Detailed analysis of the magnetic properties of the Hubbard model within dynamical mean-field theory (DMFT) is presented. Using a RPA-like decoupling of two-particle propagators we derive a universal form for susceptibilities, which captures essential aspects of localized and itinerant pictures. This expression is shown to be quantitatively valid whenever long-range coherence of particle-hole excitations can be neglected, as is the case in large parts of the phase diagram where antiferromag- netism is dominant. The applicability of an interpretation in terms of the two archetypical pictures of…
A comparison is given of the fundamental works of S. V. Vonsovsky on the many-electron polar and s-d(f) exchange models with the subsequent development of the theory of magnetism of transition and rare earth metals and their compounds. Special attention is given to the derivation of different many-electron models (by Heisenberg, Hubbard, Anderson) and to the interrelation between them. Among the problems considered in this review, of most importance are the many-electron approaches used in the description of systems of d and f electrons, the atomic representation of X-operators, and the proble…
Problems of strongly interacting electrons can be greatly simplified by reducing them to effective quantum spin models. The initial step is renormalization of the Hamiltonian into a lower energy subspace. The positive and negative U Hubbard models are explicitely transformed into the Heisenberg and -x-xz models respectively. Basic tools of quantum magnetism are introduced and used: spin coherent states path integral, spin wave theory, and continuum theory of rotators.The last lecture concerns pseudospin approaches to superconductivity and superfluidity. The SO(3) rotator theory for the -x-xz m…
Magnetic susceptibility, M-H plot, magnetoresistance and thermoelectric power of the RuSr2Eu1.5Ce0.5Cu2O10 superconductor are measured. Values of the magnetic transition temperature Tmag, superconductivity transition temperature Tc, upper critical field Hc2, chemical potential mu, and energy width for electric conduction W(sigma) are obtained from these measurements. It has been found that Tmag = 140 K, Tc = 25 K (33 K) from susceptibility (magnetoresistance) measurements, Hc2 (0) > 32 T, mu = 8 meV, and W(sigma) = 58.5 meV. These values are compared with other ruthenate superconductors, and r…
Building on the results of Ref. \cite{faye2018phase}, which identified an antiferromagnetic and Kondo singlet phases on the Kondo-Hubbard square lattice, we use the variational cluster approximation (VCA) to investigate the competition between these phases on a two-dimensional triangular lattice with $120^{o}$ spin orientation. In addition to the antiferromagnetic exchange interaction $J_{\perp}$ between the localized (impurity) and conduction (itinerant) electrons, our model includes the local repulsion $U$ of the conduction electrons and the Heisenberg interaction $J_H$ between the impuritie…
A Kondo-lattice theory is applied to the crossover between local-moment magnetism for almost half fillings of electrons and itinerant-electron magnetism away from the half filling. In clean systems with no disorder, the bandwidth W^* of quasiparticles is non-zero and of the order of |J| at T=0K even in the limit of the half filling, with J the superexchange interaction constant between nearest neighbors. The so called Gutzwiller's term also contributes to W^* away from the half filling; it is approximately proportional to doping concentrations measured from the half filling. Magnetism is enhan…
In this contribution on the celebration of the 80th birthday anniversary of Prof. Ricardo Ferreira, we present a brief survey on the magnetism of quasi-one-dimensional compounds. This has been a research area of intense activity particularly since the first experimental announcements of magnetism in organic and organometallic polymers in the mid 80s. We review experimental and theoretical achievements on the field, featuring chain systems of correlated electrons in a special AB2 unit cell structure present in inorganic and organic compounds.
Do electrons become ferromagnetic just because of their repulisve Coulomb interaction? Our calculations on the three-dimensional electron gas imply that itinerant ferromagnetim of delocalized electrons without lattice and band structure, the most basic model considered by Stoner, is suppressed due to many-body correlations as speculated already by Wigner, and a possible ferromagnetic transition lowering the density is precluded by the formation of the Wigner crystal.
Single wall carbon nanotubes grown entirely from 13-C form an ideal system to study the effect of electron interaction on nuclear magnetism in one dimension. If the electrons are in the metallic, Luttinger liquid regime, we show that even a very weak hyperfine coupling to the 13-C nuclear spins has a striking effect: The system is driven into an ordered phase, which combines electron and nuclear degrees of freedom, and which persists up into the millikelvin range. In this phase the conductance is reduced by a universal factor of 2, allowing for detection by standard transport experiments.
Kondo systems are usually described by the interaction of strong correlation induced local moment with the highly itinerant conduction electrons. Here, we study the role of electron correlations among conduction electrons in the electronic structure of a Kondo lattice compound, Ce$_2$CoSi$_3$, using high resolution photoemission spectroscopy and {\it ab initio} band structure calculations, where Co 3$d$ electrons contribute in the conduction band. High energy resolution employed in the measurements helped to reveal signature of Ce 4$f$ states derived Kondo resonance feature at the Fermi level …
We have examined the valence-band electronic structures of gold and silver in the same column in the periodic table with nominally filled d orbitals by means of a recently developed polarization-dependent hard x-ray photoemission. Contrary to a common expectation, it is found that the 5d-orbital electrons contribute prominently to the conduction electrons in gold while the conduction electrons in silver are to some extent free-electron-like with negligible 4d contribution, which could be related to a well-known fact that gold is more stable than silver in air. The 4d electron correlation effec…
The electronic properties of the polar interface between insulating oxides is a subject of great current interest. An exciting new development is the observation of robust magnetism at the interface of two non-magnetic materials LaAlO_3 (LAO) and SrTiO_3 (STO). Here we present a microscopic theory for the formation and interaction of local moments, which depends on essential features of the LAO/STO interface. We show that correlation-induced moments arise due to interfacial splitting of orbital degeneracy. We find that gate-tunable Rashba spin-orbit coupling at the interface influences the exc…
Recently synthesised Ba4NbMn3O12 belong to cluster magnets - systems with tightly bound groups of magnetism ions, in this case Mn3 trimers. Often such magnetic clusters can be described by molecular orbitals (MO), however strong electron correlations may invalidate this description. To understand the electronic and magnetic state of Ba4NbMn3O12 we carried out ab initio calculations and show that this system is better described not in MO picture, but as a system with electrons localized on the Mn ions, with strong intra-cluster and weaker inter-cluster exchange. The calculated spin of the Mn3 t…
We have explored Pauli paramagnetism, Landau diamagnetism and de Haas-van Alphen effect in a single framework, and unified these three effects for all temperatures as well as for all strengths of magnetic field. Our result goes beyond Pauli-Landau result on the magnetism of the 3-D ideal gas of electrons, and is able to describe crossover of the de Haas-van Alphen oscillation to the saturation of magnetization. We also have obtained a novel asymptotic series expansion for the low temperature properties of the system.
To efficiently manipulate magnetism is a key physical issue for modern condensed matter physics, which is also crucial for magnetic functional applications. Most previous relevant studies rely on the tuning of spin texture, while the spin orientation is often negligible. As an exception, spin-orbit coupled $J_{\rm eff}$ states of $4d$/$5d$ electrons provide an ideal platform for emergent quantum effects. However, many expectations have not been realized due to the complexities of real materials. Thus the pursuit for more ideal $J_{\rm eff}$ states remains ongoing. Here a near-ideal $J_{\rm eff…
The magnetism of the double perovskite compounds \SLFCOx\ ($x$ = 0, 1, 2) are contrasted using magnetization, neutron diffraction and electron paramagnetic resonance with the support from density functional theory calculations. \LFCO\ is identified as a long-range ordered antiferromagnet displaying a near-room temperature transition at $T_N$ = 270~K, accompanied by a low temperature structural phase transition at $T_S$ = 200~K. The structural phase transformation at $T_S$ occurs from $R\overline{3}c$ at 300~K to $Pnma$ at 200~K. The density functional theory calculations support an insulating …
The spin-lattice relaxation time, $T_{1}$, of conduction electrons is measured as a function of temperature and magnetic field in MgB$_2$. The method is based on the detection of the $z$ component of the conduction electron magnetization under electron spin resonance conditions with amplitude modulated microwave excitation. Measurement of $T_{1}$ below $T_c$ at 0.32 T allows to disentangle contributions from the two Fermi surfaces of MgB$_{2}$ as this field restores normal state on the Fermi surface part with $π$ symmetry only.
We explore the kinetic magnetism of the infinite-$U$ repulsive Hubbard models at low hole densities on various lattices with nearest-neighbor hopping integrals modulated by a staggered magnetic flux $\pmϕ$. Tuning $ϕ$ from 0 to $π$ makes the ground state (GS) change from a Nagaoka-type ferromagnetic state to a Haerter-Shastry-type antiferromagnetic state at a critical $ϕ_c$, with both states being of kinetic origin. Intra-plaquette spin correlation, as well as the GS energy, signals such a quantum criticality. This tunable kinetic magnetism is generic, and appears in chains, ladders and two-di…
The lecture introduces a reader to the relatively young field of physics of strongly interacting and disordered 2D electron system, in particular, to the phenomena of the metallic conduction and the apparent metal-insulator transition in 2D. The paper briefly overviews the experimental data on the electron transport, magnetotransport, spin-magnetization in 2D, and on the electron-electron interaction effects.
We calculate the effect of local magnetic moments on the electron-phonon coupling in BaFe$_{2}$As$_{2}+δ$ using the density functional perturbation theory. We show that the magnetism enhances the total electron-phonon coupling by $\sim 50%$, up to $λ\lesssim 0.35$, still not enough to explain the high critical temperature, but strong enough to have a non-negligible effect on superconductivity, for instance, by frustrating the coupling with spin fluctuations and inducing order parameter nodes. The enhancement comes mostly from a renormalization of the electron-phonon matrix elements. We also in…
High-quality (001)-oriented (pseudo-cubic notation) ferromagnetic YTiO$_3$ thin films were epitaxially synthesized in a layer-by-layer way by pulsed laser deposition. Structural, magnetic and electronic properties were characterized by reflection-high-energy-electron-diffraction, X-ray diffraction, vibrating sample magnetometry, and element-resolved resonant soft X-ray absorption spectroscopy. To reveal ferromagnetism of the constituent titanium ions, X-ray magnetic circular dichroism spectroscopy was carried out using four detection modes probing complimentary spatial scale, which overcomes a…
Ferromagnetism and superconductivity are in most cases adverse. However, recent experiments reveal that they coexist at interfaces of LaAlO3 and SrTiO3. We analyze the magnetic state within density functional theory and provide evidence that magnetism is not an intrinsic property of the two-dimensional electron liquid at the interface. We demonstrate that the robust ferromagnetic state is induced by the oxygen vacancies in SrTiO3- or in the LaAlO3-layer. This allows for the notion that areas with increased density of oxygen vacancies produce ferromagnetic puddles and account for the previous o…
