Combining optical and magnetic functionalities into memristors is an attractive option to expand applications into image recognition, information storage, and low power processing. Here, we have fabricated ferromagnetic-fullerene-manganese oxide structures that display a hysteretic, nonlinear I-V characteristic and a photovoltaic effect with a photocurrent dependent on the relative alignment of the magnetization and the light polarization vector. Reversible, voltage-induced oxygen migration from manganese oxide into the molecular layer reduces the resistivity of the device by several orders of magnitude, eliminates the nonlinear transport, and quenches the photovoltaic response, giving rise to an optically sensitive memristor where the photocurrent is dependent on both the electrical and magnetic history of the device. Density functional theory calculations attribute the origin of these effects to changes in the electronic structure at the Fermi level and a reduction of the interface dipole upon ionic migration. These results open research pathways towards single-molecule scale memristive memories with optical excitation, electrical readout and magnetic sensing functionalities.

We studied the displacement of magnetic domains under temperature gradients in perpendicularly magnetized Ta/[Pt/Co68B32/Ir]x10/Pt multilayer tracks with microfabricated Pt heaters and thermometers by magnetic force microscopy. Subtracting out the effects of the Oersted field from the heating current reveals the pure temperature gradient driven motion, which is always toward the heater. The higher the thermal gradient along the track is (owing to the proximity to the heater or larger heater currents), the greater the observed displacements of the domains are, up to a velocity of around 1 nm/s in a temperature gradient of 20 K/mu m. This velocity lies in the creep regime. Quantitative estimates of the strength of different driving mechanisms for the effect that have been proposed theoretically show that entropic forces dominate over those arising from the spin Seebeck and spin-dependent Seebeck effects in driving the domain motion.

Magnetic multilayers with structural inversion asymmetry, perpendicular magnetic anisotropy (PMA), and large Dzyaloshinskii-Moriya interaction (DMI) are widely studied for magnetic domain wall- and skyrmion-based data processing applications. In this work, we report a controlled, nonvolatile, but reversible local modification of such a system by electrically driven oxygen migration through the metallic film structure by using ionic liquid gating. Our findings provide direct evidence for the modification of the oxidation state at the heavy metal (HM)/ferromagnet (FM) interface. As a result, we observed changes in fundamental magnetic properties, such as an increase in the effective anisotropy constant (Keff) and coercive field (Hc) with oxidation, and a decrease with the reduction of oxygen ions. Positive gate voltages relative to the thin film extract oxygen ions from the magnetic layer, significantly reducing the domain nucleation field. In contrast, negative voltages drive oxygen ions into the magnetic layer, leading to a reversible increase in the extent of domain wall pinning near saturation. We observe a corresponding decrease in the magnetic moment and DMI, with negative voltage reducing both. This magneto-ionic modulation in fully metallic structures is beneficial for spintronic device applications, particularly in field-programmable domain wall and skyrmion devices.

We report a comprehensive temperature-dependent investigation of spin-orbit torque (SOT) generation in heterostructures comprising a perpendicularly magnetized metallic multilayer grown on top of a topological insulator (TI) epilayer. Temperature-dependent second-harmonic Hall measurements reveal distinct trends in the magnitude of the spin-orbit torque across the studied heterostructures. Samples incorporating Bi2Se3 exhibit torques reaching approximately 12 mT/(10^12 A m^-2) at 15 K, around 5 times larger than those in a multilayer without the topological layer. The structure with a thin 2-nm Ta buffer for the multilayer shows the strongest enhancement and a pronounced increase at low temperatures, highlighting efficient spin-current generation from the topological surface states. In contrast, the sample with a 10 nm-thick Ta spacer exhibits reduced torque efficiency, consistent with partial attenuation of spin transmission through the buffer. Systems lacking Bi2Se3 but containing two heavy metals (Ta and Pt) yield significantly smaller torques, around 2.5 mT/(10^12 A m^-2), despite the presence of conventional spin Hall sources. These observations underscore the dominant role of TI-derived spin-momentum-locked currents in driving large damping-like torques and their sensitivity to interfacial structure and buffer-layer thickness.

Altermagnets host spin-split electronic bands without net magnetization, enabling spin-polarized transport in the absence of conventional ferromagnetism. RuO_2 has been proposed as a candidate altermagnet, yet experimental reports remain conflicting, particularly between bulk-sensitive probes and thin-film measurements. Here we investigate the electronic transport properties of epitaxial RuO_2 thin films using anomalous Hall effect measurements and point-contact Andreev reflection spectroscopy. We observe transport spin polarization and a strongly orientation-dependent anomalous Hall response, while magnetometry reveals no detectable net magnetization. The anomalous Hall effect appears only in ultrathin (110)-oriented films, consistent with symmetry-driven Néel-vector physics, and the measured transport spin polarization is systematically higher for (110)-oriented films than for (001)-oriented films, consistent with the crystallographic anisotropy of the spin-split bands. These results are consistent with altermagnetic behavior in RuO_2, with the experimentally accessible signatures confined to near-surface regions. They also establish superconducting transport spectroscopy as a metrology for identifying and characterizing altermagnet candidates.

Information can be stored in magnetic materials by encoding with the direction of the magnetic moment of elements. A figure of merit for these systems is the energy needed to change the information rewrite the storage by changing the magnetic moment. Organic molecules offer a playground to manipulate spin order, with metallo molecular interfaces being a promising direction for sustainable devices. Here, we demonstrate a spin reorientation transition in molecular interfaces of high magnetisation 3d ferromagnetic films due to a competition between a perpendicular magnetic anisotropy (PMA) induced by a heavy metal that dominates at high temperatures, and an in-plane anisotropy generated by molecular coupling at low temperatures. The transition can be tuned around room temperature by varying the ferromagnet thickness (1.4 to 1.9 nm) or the choice of molecular overlayer, with the organic molecules being C60, hydrogen and metal (Cu, Co) phthalocyanines. Near the transition temperature, the magnetisation easy axis can be switched with a small energy input, either electrically with a current density of 10^5 A per cm2, or optically by a fs laser pulse of fluence as low as 0.12 mJ per cm2, suggesting heat assisted technology applications. Magnetic dichroism measurements point toward a phase transition at the organic interface being responsible for the spin reorientation transition.

Frustrated Kondo spin lattice (KSL) systems away from the antiferromagnetic (AFM) ground state have been found to display strange metal behaviour. A signature of strange metals in correlated systems is large Nernst response. Metallo-molecular interfaces of supramolecular lattices have been demonstrated as 2D KSL systems in STM studies. Here going beyond STM experiments we report a frustrated AFM state on molecular interfaces of Pt(111) and Pt(111)/Co films with around room temperature spin freezing transitions. Near these transitions we measure an anomalous Nernst coefficient of at least 3 μV/K.

Ba2MnTeO6 was first characterised using X-ray diffraction and reported to show a small distortion1 from the idealised cubic perovskite which displays face-centred cubic arrangement of Mn2+. A recent report has asserted that this leads to a layered configuration of Mn2+ that serves as an example of a triangular lattice, i.e. a 2D structure containing discreet layers.2 Here we show how neutron scattering gives great confidence in establishing the crystal structure being an undistorted cubic phase and how this can be mis-assigned as a triangular layered structure. This has profound implications for the understanding of the magnetic properties of the system.

Single-phase multiferroics (MFs) exhibiting ferroelectricity and ferromagnetism and the strong magnetoelectric (ME) coupling effect at room temperature are seen as key to the development of the next-generation of spintronic devices, multi-state memories, logic devices and sensors. Herein, the single-tetragonal phase (1–x) (Sr0·3Bi0·35Na0·329Li0.021)TiO3-xBiFeO3 (x = 0.2 or 0.4) system was designed to study the intrinsic ME coupling effect at room temperature and high frequencies. The polarization arises from the cooperative displacement of both Fe3+ and Ti4+ relative to the oxygen sublattice in the tetragonally distorted perovskite structure, and the magnetization stems from indirect exchange magnetic interaction between adjacent iron ions. A switchable voltage-controlled magnetization was confirmed by a change of the coercive magnetic field, Hc, and remnant magnetization, Mr, in the x = 0.4 component subjected to an external electric field at room temperature and was possibly attributed to a strain-mediated ME coupling effect. In addition, resonance behaviours of the complex magnetic permeability and complex dielectric permittivity in the GHz band indicate that this ME effect is intrinsic in nature and could broaden the applications of multiferroics to devices operating at microwave frequencies.

An exotic range of magnetic (and other) properties have been observed in A2Mo3O8 materials (where A is a single or mix of transition metals) making understanding their chemistry and physics timely. We have investigated the structural-property relationships in Mn2Mo3O8 and the related materials, MnFeMo3O8, MnCoMo3O8 and MnZnMo3O8. We report a detailed powder diffraction analysis confirming ferrimagnetic structures for Mn2Mo3O8 and MnFeMo3O8. Differing rates of spin ordering on crystallographically distinct sites (tetrahedral or octahedral) gives rise to magnetic hysteresis, which abruptly disappears in 2 K data. This appears to be correlated with ion displacement and/or electrostriction effects, which also relax at 2 K. We confirm an antiferromagnetic structure type for MnCoMo3O8 and no discernible magnetic ordering within the temperature range studied for MnZnMo3O8. For MnZnMo3O8 we suggest a small amount of site disorder acts to suppress magnetic ordering. This suggests that magnetic properties can be tuned both through A-site cation order and choice of A-site cations.

This study investigates the effects of incorporating 11B4C interlayers into Fe/Si multilayers, with a focus on interface quality, reflectivity, polarization, and magnetic properties for polarizing neutron optics. It is found that the introduction of 1-2 & Aring; 11B4C interlayers significantly improves the interface sharpness, reducing interface width and preventing excessive Si diffusion into the Fe layers. X-ray reflectivity and polarized neutron reflectivity measurements show enhanced reflectivity and polarization, with a notable increase in polarization for 30 & Aring; period multilayers. The inclusion of interlayers also helps prevent the formation of iron-silicides, improving both the magnetic properties and neutron optical performance. However, the impact of interlayers is less pronounced in thicker-period multilayers (100 & Aring;), primarily due to the ratio between layer and interface widths. These results suggest that 11B4C interlayers offer a promising route for optimizing Fe/Si multilayer performance in polarizing neutron mirrors.

An electric bias can shift the Fermi level along the Dirac cone of a topological insulator and modify its charge transport, but tuning the electronic states and spin-orbit interaction (SOI) without destroying the surface topology is challenging. Here, we show that thin film Bi2Se3/n-p (p-n) molecular diodes form ordered interfaces where charge transfer and orbital re-hybridisation result in a decrease (increase) of the carrier density and improved mobility. In Bi2Se3 the spin-orbit lifetime, t_so, is 0.13 ps, which is comparable to the strongest spin-orbit materials. This lifetime drops further to 0.06 ps (0.09 ps) with the addition of p-n (n-p) molecular diodes, at the limit of measurable values. This strengthened spin-orbit interaction occurs even though molecules are made of light elements and increase the mean free path of the charge carriers by almost 50

Even though abundant research has focused on metamagnetic critical end points in itinerant magnets, this critical phenomenon for magnetic insulators is still to be explored extensively. DyVO4, a magnetic insulator exhibits a field induced first order metamagnetic transition (MMT), which has previously been investigated via thermodynamic measurements. In this work, we extend our investigations down to mK temperatures and probe the metamagnetic tricritical point (TCP) directly via the magnetocaloric effect (MCE). Heat capacity reveals an inimitable phase diagram where the second order antiferromagnetic phase transition terminates at the TCP, beyond which it continues as a line of first order MMT as the temperature is lowered towards 0 K. The sample temperature and magnetic Gr & uuml;neisen parameter (Pm) evaluated from MCE data show direct evidence of critical fluctuations and enhanced entropy in the vicinity of the TCP. These fluctuations are also supported by diverging susceptibility observed near the TCP. Critical analysis of magnetization suggests that the metamagnetic TCP in DyVO4 does not belong to any universal class. However, the extracted exponents agree with another insulating metamagnet, HoMnO3 [Phys. Rev. Lett. 110, 157202 (2013)], suggesting the presence of a unique universality class for metamagnetic critical systems.

Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP3SiO11. We confirm the requisite j eff = 1 2 state of Ru3+ in RuP3SiO11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model.

The strong exchange interaction between 3d-4f magnetic sublattice in rare-earth perovskites introduces a variety of complex magnetic states hosting fascinating electronic ground states with exotic properties. Especially when it comes to rare-earth nickelate and cobaltite perovskites, tuning their rich magnetic phase diagram and spin-state transitions make them potential candidates for spintronic applications. Here, we report the observation of antiferromagnetic coupling between Pr 4f and Ni/Co 3d magnetic sublattices and its tunability with strain in PrCo_0.5Ni_0.5O_3-δ (PCNO) thin films. SQUID magnetization measurements reveal ferromagnetic (FM) ordering around 25 K, followed by a spin glass transition at low temperatures subject to spin reorientation. Competing magnetic interactions arise owing to the 3d-4f antiferromagnetic (AFM) coupling between Pr and Co/Ni sublattice as revealed by the X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) at the Pr M_4,5 and Co/Ni L_2,3 absorption edges. Strain dependence on these AFM coupling reveals an increase (decrease) in the AFM exchange interaction for tensile (compressive) strained films, leading to a net decrease (increase) in the magnetization of PCNO films at low temperatures. The relative increase in low-temperature negative magnetoresistance for compressively strained films also reflects the enhanced ferromagnetic ordering in the system. The angle-dependent magnetoresistance measurements reveal a two-fold anisotropic magnetoresistance (AMR) in tensile strained PCNO films. In contrast, temperature-dependent switching of AMR accompanied by a two- to four-fold symmetry crossover is observed for LaAlO_3-grown compressive strained films.

Abstract Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP3SiO11. We confirm the requisite $${j}_{{\mathsf{eff}}}=\frac{1}{2}$$ j eff = 1 2 state of Ru3+ in RuP3SiO11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model.

The magnetic properties of a 2D layered material consisting of high-spin Co2+ complexes, [Co(NH3NH2)(2)(H2O)(2)Cl-2]Cl-2 (CoHyd(2)Cl(4)), have been extensively characterized using electron paramagnetic resonance, magnetic susceptibility, and low-temperature heat capacity measurements. Electron paramagnetic resonance spectroscopy studies suggest that below 50 K, the J = 3/2 orbital triplet state of Co is gradually depopulated in favor of the J = 1/2 spin state, which is dominant below 20 K. In light of this, the magnetic susceptibility has been fitted with a two-level model, indicating that the interactions in this material are much weaker than previously thought. This two-level model is unable to fit the data at low temperatures and, combined with electron paramagnetic resonance spectroscopy, suggests that ferromagnetic interactions between Co2+ cations in the J = 1/2 state become significant approaching 2 K. Heat capacity measurements suggest the emergence of a long-range ordered state below 246 mK, which neutron diffraction confirms to be ferromagnetic.

We present a comprehensive study of PrIr3B2, which includes a detailed investigation of its crystal and magnetic structure using neutron diffraction. AC and DC magnetization and heat capacity data reveal antiferromagnetic ordering atTN= 10 K. The heat capacity measurements further exhibit a broad peak near 270 K which is related to a structural transition fromP6/mmmtoC2/mseen in low temperature x-ray diffraction and neutron diffraction. High intensity neutron diffraction data confirm the long-range ordering of Pr3+spins, with no apparent magnetic moment on either of the Iridium sites. Two possible magnetic structures with eitherk1= [1,0,0] ork2= [½,½,0] fit nearly equally well the neutron diffraction data. However, based on previous magnetization studies on a single crystalline sample it is argued that the second solution withk2corresponds to the appropriate magnetic structure of PrIr3B2below 10 K. In this magnetic structure, the Pr3+moments are oriented at ∼45° to both theaandbaxes, with thec-axis being the hard axis of magnetization. Overall, our results provide new insights into the magnetic and structural properties of PrIr3B2.

Studies of ferromagnet-superconductor hybrid systems have uncovered magnetic interactions between the competing electronic orderings. The electromagnetic (EM) proximity effect predicts the formation of a spontaneous vector potential inside a superconductor placed in proximity to a ferromagnet. In this work, we use a Nb superconducting layer and Ni ferromagnetic layer to test for such magnetic interactions. We use the complementary, but independent, techniques of polarised neutron reflectometry and detection Josephson junctions to probe the magnetic response inside the superconducting layer at close to zero applied field. In this condition, Meissner screening is negligible, so our measurements examine only additional magnetic and screening contributions from proximity effects. We report the absence of any signals originating from EM proximity effect in zero applied field. Our observations indicate that either EM proximity effect is below the detection resolution of both of our experiments or may indicate a new phenomenon that requires extension of current theory. From our measurements, we estimate a limit of the size of the zero field EM proximity effect in our Ni-Nb samples to be $\pm0.27$ mT.