We analytically solve the Landau-Lifshitz equations for the collective magnetization dynamics in a synthetic antiferromagnet (SAF) nanoparticle and uncover a regime of barrier-free switching under a short small-amplitude magnetic field pulse applied perpendicular to the SAF plane. We give examples of specific implementations for forming such low-power and ultra-fast switching pulses. For fully optical, resonant, barrier-free SAF switching we estimate the power per write operation to be ∼100 pJ, 10–100 times smaller than for conventional quasi-static rotation, which should be attractive for memory applications.

Magnetic properties of Y3AlFe4O12 garnet ceramics have been studied over a wide range of temperature (3 – 370 K) and magnetic fields (up to 2 kOe). Effects of varying the temperature on some of the application-specific magnetic characteristics have been analyzed in detail. With the decrease in temperature, the effective anisotropy constant, KEff, is found to sharply rise below ∼150 K, while the saturation magnetization, Ms, changes only slightly (<20 % within 3 – 250 K). The exchange stiffness, Aex, and spin wave stiffness, D, parameters mirror the relatively smooth behavior of the magnetization at low temperatures but display a rapid drop when T approaches TC ≈ 436 K. The temperature dependence of the domain wall thickness and the critical single-domain size correlate with the corresponding values for pure Y3Fe5O12 (YIG) and are in agreement with the theoretical estimates. We conclude by discussing the ways of how to use the obtained results for tailoring the magnetic properties of YIG-based materials for technological applications.

The dynamic magnetic properties of full Heusler alloy thin films of Co 2 FeGe, grown on MgO (001) substrates under different thermal conditions, were investigated. Brillouin light scattering and ferromagnetic resonance measurements revealed that depositing at room temperature followed by annealing at 300 ° C for 1 h produces the best results for maximizing magnetization, exchange stiffness, and minimizing spin-dynamic dissipation in the films, which are desirable characteristics for high-speed spintronic devices. Additionally, strong hybridization of spin waves in the Damon-Eshbach geometry was observed, which is attractive for applications in magnonic signal processing circuits.

We demonstrate a method of obtaining tunable magnetic anisotropy inCu-Al-Mn shape memory alloys, consisting of aging the material in a magnetic field of 1.5 KOe at elevated temperature ofT=200°C for the precipitation of ferromagnetic nanoparticle of an elongated shape. Using a combination of magnetic and structural measurements, the structural phase transformations of a martensitic type and paramagnetic-superparamagnetic-spin glass transitions were studied in a wide temperature range. On magnetic field aging, a decrease in magnetization and an increase in coercivity are observed, accompanied by a slight shift in the temperature of the magnetic and martensitic phase transition. The observed changes in the magnetic properties of the nanostructured material are explained by additional induced magnetic anisotropy resulting from such thermomagnetic treatment.

We present the results of experimental studies of the influence of an external magnetic field on the structural characteristics (surface roughness and structural entropy) of nanogranular thin-film system based on Co and Cu. The samples CoxCu100-x in a wide range of compositions (17 at. % ≤ x ≤ 69 at. %) with the thickness of d = 35 nm were obtained by electron-beam co-evaporation using two independent electron guns. After obtaining, the films were annealed in a vacuum at a temperature of 800 K for 30 min. The studies of magnetoresistive properties have shown that the maximum giant magnetoresistance (GMR) amplitude (1.7 % in the transverse and 1.6 % in the longitudinal measurement geometries) in a magnetic field of H = 4.5 kOe at room temperature was observed in the Co21Cu79 film alloy. Transmission electron microscopy showed that this sample contains hcp-Co granules with a size of L = 5 ÷ 12 nm in a matrix of metastable fcc-Cu(Co) solid solution. The influence of the external magnetic field on the structural characteristics and surface morphology of the Co21Cu79 thin-film alloy was investigated using atomic force microscopy (AFM). It was found that a first impact of application of external magnetic field with H = 0.5 kOe causes a decrease in the values of the arithmetic mean Ra, and quadratic mean Rq, of the film roughness and structural entropy S. A decreases in Ra by 8.5 %, Rq by 6.5 %, and structural entropy S by 6.5 % were observed. After application of a larger magnetic field with H = 1.0 kOe and during the subsequent relaxation of the structure within 15 h after the field is turned off, the values of the structural parameters of the film surface did not change significantly.

Two series of isostructural intermetallics have been discovered in our search for new compounds with fused honeycomb motifs, both stable at elevated temperatures (1073 K). They crystallize with orthorhombic unit cells - La4Co4M (M = Sn, Sb, Te, Pb, Bi, SG Pbam, a = 8.247-8.315(2), b = 21.913-22.137(7), c = 4.750-4.664(2) angstrom, V = 850.5-869.5(4) angstrom 3, Z = 4) and La3Ni3M (M = Al, Ga, SG Cmcm, a = 4.1790-4.2395(1), b = 10.4921-10.6426 (6), c = 13.6399-13.7616(8) angstrom, V = 606.72-612.05(7), Z = 3). The crystal structures represent interesting variations of semiregular tilings of corrugated anionic layers and predominantly cationic zigzag motifs. The La4Co4M compounds reveal a complex type of ordering with a high degree of frustration as could be expected for the Kagome ' -related lattices, while magnetic ordering in the La3Ni3M series is less evident. Electronic structure calculations have been performed for multiple compounds within both series revealing metallic character and visible local minima around the Fermi level. The bonding picture is characterized by nearly equal contributions from the anionic and the cationic components.

We investigate the switching of a magnetic nanoparticle comprising the middle free layer of a memory cell based on a double magnetic tunnel junction under the combined effect of spin-polarized current and weak on-chip magnetic field. We obtain the timing and amplitude parameters for the current and field pulses needed to achieve 100 ps range inertia-free switching under least-power dissipation. The considered method does not rely on the stochastics of thermal agitation of the magnetic nanoparticle typically accompanying spin-torque switching. The regime of ultimate switching speed efficiency found in this work is promising for applications in high-performance nonvolatile memory.

We present all-electrical operation of a FexCr1-x-based Curie switch at room temperature. More specifically, we study the current-induced thermally driven transition from ferromagnetic to antiferromagnetic Magnetometry measurements at different temperatures show that the transition from the ferromagnetic to the antiferromagnetic coupling at zero field is observed at approximately 325 K. Analytical modeling confirms that the observed temperature-dependent transition from indirect ferromagnetic to indirect antiferromagnetic interlayer exchange coupling originates from the modification of the effective interlayer exchange constant through the ferromagnetic-to-paramagnetic transition in the Fe17.5Cr82.5 spacer with minor contributions from the thermally driven variations of the magnetization and magnetic anisotropy of the Fe layers. Room-temperature current-in-plane magnetotransport measurements on the patterned Fe/Cr/Fe17.5Cr82.5/Cr/Fe strips show the transition from the "low-resistance" parallel to the "highresistance" antiparallel remanent magnetization configuration, upon increased probing current density. Quantitative comparison of the switching fields, obtained by magnetometry and magnetotransport, confirms that the Joule heating is the main mechanism responsible for the observed current-induced resistive switching.

We investigate the interlayer coupling between two thin ferromagnetic (F) films mediated by an antiferromagnetic (AF) spacer in F∗/AF/F trilayers and show how it transitions between different regimes on changing the AF thickness. Employing layer-selective Kerr magnetometry and ferromagnetic-resonance techniques in a complementary manner enables us to distinguish between three functionally distinct regimes of such ferromagnetic interlayer coupling. The F layers are found to be individually and independently exchange-biased for thick FeMn spacers - the first regime of no interlayer F-F∗ coupling. F-F∗ coupling appears on decreasing the FeMn thickness below 9 nm. In this second regime found in structures with 6.0-9.0-nm-thick FeMn spacers, the interlayer coupling exists only in a finite temperature interval just below the effective Néel temperature of the spacer, which is due to magnon-mediated exchange through the thermally softened antiferromagnetic spacer, vanishing at lower temperatures. The third regime, with FeMn thinner than 4 nm, is characterized by a much stronger interlayer coupling in the entire temperature interval, which is attributed to a magnetic-proximity induced ferromagnetic exchange. These experimental results, spanning the key geometrical parameters and thermal regimes of the F∗/AF/F nanostructure, complemented by a comprehensive theoretical analysis, should broaden the understanding of the interlayer exchange in magnetic multilayers and potentially be useful for applications in spin thermionics.

Sr2FeMoO6 granular structure with dielectric SrMoO4 grain interfaces was synthesized by citrate sol–gel method. The sample annealed in Ar/O2 flow at 700 K for 5 h demonstrated semiconducting-like behavior. Detailed analysis of temperature dependent electrical resistivity showed that conduction process occurs due to variable range hopping electron transfer through defect states in the dielectric SrMoO4 layers. Two mechanisms of hopping are realized depending on temperature. The current–voltage characteristics and magnetoresistance were studied and analyzed.