Single-layer vanadium nitride (VN) and bilayer Pd
0.96
Fe
0.04
/VN and VN/Pd
0.92
Fe
0.08
thin-film heterostructures for possible spintronics applications were synthesized on (001)-oriented ...single-crystalline magnesium oxide (MgO) substrates utilizing a four-chamber ultrahigh vacuum deposition and analysis system. The VN layers were reactively magnetron sputtered from a metallic vanadium target in Ar/N
2
plasma, while the Pd
1−
x
Fe
x
layers were deposited by co-evaporation of metallic Pd and Fe pellets from calibrated effusion cells in a molecular beam epitaxy chamber. The VN stoichiometry and Pd
1−
x
Fe
x
composition were controlled by X-ray photoelectron spectroscopy. In situ low-energy electron diffraction and ex situ X-ray diffraction show that the 30 nm thick single-layer VN as well as the double-layer VN(30 nm)/Pd
0.92
Fe
0.08
(12 nm) and Pd
0.96
Fe
0.04
(20 nm)/VN(30 nm) structures have grown cube-on-cube epitaxially. Electric resistance measurements demonstrate a metallic-type temperature dependence for the VN film with a small residual resistivity of 9 μΩ·cm at 10 K, indicating high purity and structural quality of the film. The transition to the superconducting state was observed at 7.7 K for the VN film, at 7.2 K for the Pd
0.96
Fe
0.04
/VN structure and at 6.1 K for the VN/Pd
0.92
Fe
0.08
structure with the critical temperature decreasing due to the proximity effect. Contrary to expectations, all transitions were very sharp with the width ranging from 25 mK for the VN film to 50 mK for the VN/Pd
0.92
Fe
0.08
structure. We propose epitaxial single-crystalline thin films of VN and heteroepitaxial Pd
1−
x
Fe
x
/VN and VN/Pd
1−
x
Fe
x
(
x
≤ 0.08) structures grown on MgO(001) as the materials of a choice for the improvement of superconducting magnetic random access memory characteristics.
A series of Pd1-xFex alloy epitaxial films (x = 0. 0.038. 0.062. and 0.080). a material promising for superconducting spintronics, was prepared and studied with ultrafast optical and magneto-optical ...laser spectroscopy in a wide temperature range of 4-300 K. It was found that the transition to the ferromagnetic state causes a qualitative change of both the reflectivity and the magneto-optical Kerr effect transients. A nanoscale magnetic inhomogeneity of the ferromagnet/paramagnet type inherent in the palladium-rich Pd1-xFex alloys reveals itself through the occurrence of a relatively slow. 10-25 ps. photoinduced demagnetization component following a subpicosecond one; the former vanishes at low temperatures only in the x = 0.080 sample. We argue that the 10 ps timescale demagnetization originates most probably from the diffusive transport of d electrons under the condition of nanoscale magnetic inhomogeneities. The low-temperature fraction of the residual paramagnetic phase can be deduced from the magnitude of the slow reflectivity relaxation component. It is estimated as ≈30% for x = 0.038 and ≈15% for x = 0.062 films. The minimal iron content ensuring the magnetic homogeneity of the ferromagnetic state in the Pd1-xFex alloy at low temperatures is about 7-8 atom %.
In this work, we report on the endotaxial growth of α-Fe nanoparticles in the near-surface layer under high-fluence iron ion implantation of the single-crystal magnesium oxide substrate. ...Comprehensive Mössbauer effect and magnetometry studies show that the implanted sample reveals a pronounced ferromagnetic response even at room temperature, and the α-Fe nanoparticles serve as its main source. The broad band at ~1000 Oe in the X-band magnetic resonance spectra originates from the α-Fe fraction. It manifests the properties of the easy-plane system with the four-fold in-plane anisotropy. The last indicates that the α-Fe nanoparticles are coherently incorporated into the host MgO matrix.
The results of a study of heavy implantation of a LiNbO3 crystal with iron ions are reported for the first time. The X-cut LiNbO3 substrate was implanted with 40-keV Fe+ ions to the fluence of ...1.5·1017 ions/cm2. The sample reveals pronounced ferromagnetic properties at room temperature. However, the ferromagnetic response observed in the iron-implanted LiNbO3 differs from the magnetic behavior of other oxides implanted with iron ions under the same conditions. This difference occurs from the unusual magnetic phase composition of the implanted surface layer of the LiNbO3 in which the iron implant precipitates in the form of the nanoscale alloy of metallic iron with niobium. Based on Mössbauer spectroscopy data, we estimated the Nb content in the ion-synthesized nanosized alloy as ~12 at.%, which is much higher than the solid solubility limit of Nb in bulk Fe.
We have investigated the low-temperature magnetoresistive properties of a thin epitaxial Pd0.92Fe0.08 film at different directions of the current and the applied magnetic field. The obtained ...experimental results are well described within an assumption of a singledomain magnetic state of the film. In a wide range of the appled field directions, the magnetization reversal proceeds in two steps via the intermediate easy axis. An epitaxial heterostructure of two magnetically separated ferromagnetic layers. Pd0.92Fe0.08/Ag/ Pd0.96Fe0.04. was synthesized and studied with de magnetometry. Its magnetic configuration diagram has been constructed and the conditions have been determined for a controllable switching between stable parallel, orthogonal, and antiparallel arrangements of magnetic moments of the layers.
This work is devoted to an investigation of the magnetic properties and thermal behaviour of the natural oxoborates vonsenite and hulsite in the temperature range 5–500 K. The local environment, the ...oxidation states of the Fe and Sn atoms, and the charge distribution were determined using Mössbauer spectroscopy and are in accordance with a refinement of the crystal structure of hulsite from single‐crystal X‐ray diffraction data (SCXRD) in anisotropic approximation for the first time. The magnetic properties were studied by vibrating sample magnetometry (VSM) (5 ≤ T ≤ 400 K) and are reported for the first time for iron‐rich hulsite. Both oxoborates show a very complex magnetic behaviour. Cascades of magnetic transitions are revealed and the critical temperatures were determined. The sequences of magnetic transitions in both vonsenite and hulsite with increasing temperature were found to be as follows: magnetically ordered state → partial magnetic ordering → paramagnetic state. According to X‐ray diffraction data (93 ≤ T ≤ 500 K), these processes are accompanied by anomalies in the unit‐cell parameters and thermal expansion of the oxoborates at critical temperatures. A strong negative volume thermal expansion is observed for both oxoborates at temperatures below ∼120 K.
Vonsenite and hulsite were investigated by a set of in situ low‐temperature methods. Cascades of magnetic transitions were revealed in both oxoborates and the critical temperatures were determined. Anomalies in the unit‐cell parameters and thermal expansion of the oxoborates at critical temperatures were observed.
We present the results of a successful synthesis and investigation of polycrystalline Fe2+(Cr3+, Fe3+)2O4 powder, where 1/8 part of the Cr3+ ions in the octahedral sites is substituted by the Fe3+ ...ones. It is shown that under such doping, the material retains the cubic spinel structure characteristic of the parent FeCr2O4 compound. However, the values of the critical temperatures have changed. Both the orbital and magnetic orderings occur at about 120 K, and magnetic structure rearrangement associated with an onset of spiral modulation takes place at 26 K. Mössbauer studies in a wide temperature range make it possible to accurately control the content of iron ions, their valence and magnetic states, and local environment, therefore, allowing a deeper understanding of the features of the revealed transformations.
Thin epitaxial films of the palladium-rich Pd
1−
x
Fe
x
alloy were synthesized and extensively studied as a tunable ferromagnetic material for superconducting spintronics. The (001)-oriented MgO ...single-crystal substrate and the composition range of
x
= 0.01–0.07 were chosen to support the epitaxial growth and provide the films with magnetic properties spanning from very soft ferromagnet for memory applications to intermediately soft and moderately hard for the programmable logic and circuit biasing, respectively. Dependences of the saturation magnetization, Curie temperature and three magnetic anisotropy constants on the iron content
x
were obtained for the first time from the analyses of the magnetometry and ferromagnetic resonance data. The experimental results were discussed based on existing theories of dilute ferromagnetic alloys. Simulation of the hysteresis loops within the Stoner-Wohlfarth model indicates the predominant coherent magnetic moment rotation at cryogenic temperatures. The obtained results were compiled in a database of magnetic properties of a palladium-iron alloy in a single-crystal thin-film form considered as a material for superconducting spintronics.
Relevance of the work is caused by the need to study the environmental consequences of long-term transboundary transport of pollutants from industrial centers of East Kazakhstan to the Altai region ...and Altai Republic. The main aim of the research is to study the elemental composition and features of its distribution in the epilitic lichen Rhizocarpon geographicum (L.) DC. on stone as a biogeochemical indicator of the specificity and intensity of transboundary transport of pollutants to the Altai territory. The methods: selection of samples of lichen Rhizocarpon geographicum (L.) DC. on rock outcrops of lower Paleozoic terrigenous rocks to determine the content of mercury and 28 chemical elements by atomic absorption and instrumental neutron activation analysis, processing the data by methods of applied statistics. The results. The authors have obtained the data on the levels of content and distribution characteristics of the complex chemical elements in the lichen Rhizocarpon geographicum (L.) DC. on stone on the territory of Altai. They were compared with the regional background and Clark in the biosphere. The presence of two groups of elements in the lichen – trace elements of inorganic dust and the Association of elements of polymetallic ores (Zn, As, Sb, Br, Hg, Au) was established. The argument in favor of the predominant receipt of elements of this Association in the lichen Rhizocarpon from atmospheric deposition transferred from the territory of East Kazakhstan was given. The authors identified the large area of elevated concentrations of the studied elements in Rhizocarpon, spatially coinciding with the previously established area of snow and vegetation contamination in the region. They made the conclusion on suitability of the elemental composition of epilitic lichen Rhizocarpon on stone as a biogeochemical indicator of the specificity and intensity of transboundary transport of pollutants to the Altai territory.
We have investigated the low-temperature magnetoresistive properties of a thin epitaxial Pd
Fe
film at different directions of the current and the applied magnetic field. The obtained experimental ...results are well described within an assumption of a single-domain magnetic state of the film. In a wide range of the appled field directions, the magnetization reversal proceeds in two steps via the intermediate easy axis. An epitaxial heterostructure of two magnetically separated ferromagnetic layers, Pd
Fe
/Ag/Pd
Fe
, was synthesized and studied with dc magnetometry. Its magnetic configuration diagram has been constructed and the conditions have been determined for a controllable switching between stable parallel, orthogonal, and antiparallel arrangements of magnetic moments of the layers.
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