Magnetic properties of lattice imperfections in alkali halide single crystals.
Magnetic properties of lattice imperfections in lithium fluoride, potassium chloride and sodium chloride single crystals
MAGNETIC PROPERTY↗
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Control over the Magnetic Properties of Co/Pt-based Multilayered Periodical Structures
The possibility of controlling the magnetic properties of multilayered periodical structures with perpendicular magnetic anisotropy, which are based on cobalt and platinum films, have been studied. The multilayered films composed by layers with a thickness of 0.5–1.0 nm were subjected to two types of actions: vacuum annealing at different temperatures and irradiation by helium ion beams. Transmission electron microscopy has shown that the irradiation by He{sup +} ions with energy of 30 keV leads to material mixing in the layers since at vacuum annealing the layered structure of films is kept. In this case, as a result of thermal annealing, the coercive force of the structure increases significantly, and upon irradiation with helium ions, the coercivity of the films decreases to a change in the type of anisotropy from perpendicular to “easy plane” anisotropy.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Modification of Magnetic Properties of a CoPt Alloy by Ion Irradiation
The effect of ion irradiation on magnetic properties of films of the ferromagnetic CoPt alloy fabricated by electron-beam evaporation has been studied. It is found that the coercive force decreases and the lateral component of the easy-magnetization axis increases as the He{sup +} ion fluence increases from 1 × 10{sup 13} to 1 × 10{sup 16} cm{sup –2}. It is shown by magnetic-force microscopy and the Mandelstam–Brillouin spectroscopy that the formation of isolated circle domains which are magnetic skirmions in the CoPt layer is activated at certain ion-irradiation fluence (3 × 10{sup 14} cm{sup –2}).
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Soft Magnetic Properties of Hf{sub x}Co{sub 100−x} Thin Films
Hf{sub x}Co{sub 100−x} thin films (in the atomic weight range of x = 30–36) were growth on Si (100) substrates by direct current (DC) magnetron sputtering method. Thin films produced with atomic compositions in this context depicted the amorphous structure. The films revealed soft magnetic properties and thus exhibited very low hysteresis along the hard-axis direction. Magnetic measurements indicated that Hf{sub 35}Co{sub 65} thin film has the maximum saturation magnetization (1491 emu cm{sup −3}) at 300 K. Additionally, magnetization measurements show an increase in saturation magnetization value from 981 to 1491 emu cm{sup −3} when the value of x varies between 30 and 35. The influence of varying sputtering pressure and film composition on soft magnetic properties are investigated and discussed in the present paper.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Magnetic properties of nearly stoichiometric CeAuBi{sub 2} heavy fermion compound
Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX{sub 2} (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu{sub 1−x}Bi{sub 2−y} by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu{sub 1−x}Bi{sub 2−y} (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at T{sub N} = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (H{sub c} ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu{sub 0.92}Bi{sub 1.6} exhibits a weak heavy fermion behavior with strongly localized Ce{sup 3+} 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J{sub RKKY} exchange parameters between the Ce{sup 3+} ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu{sub 1−x}Bi{sub 2−y} compounds, and we compare our results with the isostructural compound CeCuBi{sub 2}.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of calcination temperature on microstructure and magnetic properties of Ni{sub 0.5}Zn{sub 0.25}Cu{sub 0.25} Fe{sub 2}O{sub 4} nanoparticles synthesized by sol-gel method
This paper examines the effect of calcination process on the structural and magnetic properties material nanostructure composite of Ni{sub 0Ð}œ‡{sub 5}Zn{sub 0Ð}œ‡{sub 25}Cu{sub 0.25} Fe{sub 2}O{sub 4} ferrites. The samples were successfully prepared by sol-gel method at different calcination temperature, which are 600°C, 700°C, 800°C and 900°C. Morphological investigation, average crystallite size and microstructure of the material were examined by using X-ray diffraction (XRD) and confirmed by high resolution transmission electron microscope (HRTEM) and field emission scanning electron microscope (FESEM). The effects of calcination temperature on the magnetic properties were calculated by using vibrating sample magnetometer (VSM). The XRD result shows single-phase cubic spinel structure with interval average size 5.9-38 nm, and grain size microstructure of the material was increasing with temperature increases. The highest magnetization saturation was reached at a temperature 800°C with value 53.89 emu/g, and the value coercive force (Hc) was inversely with the grain size.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Structural and magnetic properties of FeNi thin films fabricated on amorphous substrates
FeNi films were fabricated by sputtering and rapid thermal annealing on thermally amorphous substrates to realize the formation of an L1{sub 0}-FeNi phase by a simple method. Structural and magnetic properties of FeNi films were investigated by varying the annealing temperature. L1{sub 0}-FeNi superlattice peaks were not observed in X-ray diffraction patterns, indicating no formation of L1{sub 0}-ordered phase, however, the surface structure systematically changed with the annealing temperature. Magnetization curves also revealed a drastic change depending on the annealing temperature, which indicates the close relation between the morphology and magnetic properties of FeNi films fabricated on amorphous substrates.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Tailoring the magnetic properties of new Fe-Ni-Co-Al-(Ta,Nb)-B superelastic rapidly quenched microwires
Ferromagnetic Fe-Ni-Co-Al-(Ta,Nb)-B microwires with diameters from 170 μm to 50 μm, which possess both superelastic and good magnetic properties, have been prepared by rapid quenching from the melt using the in rotating water spinning technique followed by cold-drawing and ageing. The cold-drawing and annealing processes lead to the initialization of premartensitic phases as confirmed by the X-ray diffraction and scanning transmission electron microscopic investigations, more significantly in the 50 μm cold-drawn microwires. An increase in the coercive field and in the saturation magnetization has been obtained by annealing, more importantly in the case of Nb-containing alloy. Ageing by thermal or current annealing led to the initialization of the superelastic effect. High values of strain of up to 1.8%, very good repeatability under successive loading, and values of superelastic effect of up to 1.2% have been achieved. The structural analysis coupled with the stress-strain data suggests that these materials annealed at 800 °C have superelastic potential at reduced ageing times. The magnetic behavior was found to be easily tailored through both thermal and thermomagnetic treatments with changes in the magnetic parameters which can be contactless detected. The results are important for future applications where both mechanical and magnetic properties matter, i.e., sensing/actuating systems.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effects of Lanthanum on Structural and Magnetic Properties of Sr{sub 1−x}La{sub (2/3)x}Fe{sub 12}O{sub 19} Compounds: Theoretical and Experimental Results
Pre-reacted powders of M-type strontium hexaferrites with chemical composition Sr{sub 1−x}La{sub (2/3)x}Fe{sub 12}O{sub 19} (x = 0.1, 0.2, 0.3 0.5, 0.6) were obtained from the conventional solid state reaction method. The final consolidation of these powders were performed by using the spark plasma sintering (SPS) technique. The influence of the La{sup 3+} content on the crystal structure and the magnetic properties of the samples were investigated firstly under the framework of a phenomenological model that predicted the cation substitution/distribution in the Sr and/or Fe sites. The theoretical results indicated that La{sup 3+} ion mostly occupies the Sr{sup 2+} site. It was also found that as La content increased, a certain amount of Fe{sup 2+} ions appear as a consequence of the Fe{sup 3+} to Fe{sup 2+} reduction. However, the Fe{sup 2+} occupied preferably the 12k and 4f1 iron sites. The magnetic properties of the obtained samples were assessed by measurements performed in a vibrating sample magnetometer. Also, X-ray diffraction (XRD) measurements were presented as a complementary characterization. We have found that the magnetic properties of the samples degraded as the La{sup 3+} content increased and the increase of the Fe{sub 2}O{sub 3} impurity phase.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Crystallographic and magnetic properties of the spinel-type ferrites Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 0.75)
Ultrahigh frequencies (UHF) have applications in signal and power electronics to minimize product sizes, increase production quantity and lower manufacturing cost. In the UHF range of 300 MHz to 3 GHz, ferrimagnetic iron oxides (ferrites) are especially useful because they combine the properties of a magnetic material with that of an electrical insulator. Ferrites have much higher electrical resistivity than metallic ferromagnetic materials, resulting in minimization of the eddy current losses, and total penetration of the electromagnetic (EM) field. Hence ferrites are frequently applied as circuit elements, magnetic storage media like read/write heads, phase shifters and Faraday rotators. The electromagnetic properties of ferrites are affected by operating conditions such as field strength, temperature and frequency. The spinel system Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x=0.0, 0.25, 0.50 and 0.75) has been prepared by the standard solid state sintering method. X-ray and neutron powder diffraction measurements were performed at room temperature. Neutron diffraction data analysis confirms the cubic symmetry corresponding to the space group Fd3m. The distribution of three cations Zn{sup 2+}, Co{sup 2+} and Fe{sup 3+} over the spinel lattice and other crystallographic parameters like lattice constant, oxygen position parameter, overall temperature factor and occupancies of different ions in different lattice sites for the samples have been determined from the analysis of neutron diffraction data. The lattice constant increases with increasing Zn content in the system. The magnetic structure was found to be ferrimagnetic for the samples with x≤0.50. Magnetization measurements show that with the increase of Zn content in the system the value of saturation magnetization first increases and then decreases. The variation of the magnetic moment with Zn substitution has been discussed in terms of the distribution of magnetic and non-magnetic ions over the A and B sub-lattices and their exchange coupling.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Investigation on Electronic Structures and Magnetic Properties of (Mn, Ga) Co-doped SnO{sub 2}
The electronic structures and magnetic properties of (Mn, Ga) co-doped SnO{sub 2} are studied by the first-principles calculations in full-potential linearized augmented plane wave formalism within generalized gradient approximations. We found that the doped system favors the ferromagnetic state and room-temperature ferromagnetism can be expected in it. The origin of ferromagnetism can be attributed to p-d exchange interactions as Mn-O-Mn. Ga acts as acceptor in (Mn, Ga) co-doped SnO{sub 2} host and can donate one hole, increasing the carrier concentration and thus leading to a more stable ferromagnetic state. These results suggest a recipe obtaining promising dilute magnetic semiconductor by doping nonmagnetic elements in SnO{sub 2} matrix.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of Si on the Glass Formation and Magnetic Properties of High-Iron Fe–Zr–Si Alloys
High-iron Fe–Zr–Si amorphous ribbons were fabricated through the melt-spun technique. Then, the effects of Si content on the glass-forming ability and magnetic properties of Fe{sub 90−x}Zr{sub 10}Si{sub x} (x = 1, 2, 3, 4, 5, 10) alloys were investigated. Results showed that the amorphous structure only formed in an alloy composition of 3 at.% Si. Moreover, α-Fe(Si) and Fe{sub 3}Zr phase appeared gradually when Si was added. Fe{sub 87}Zr{sub 10}Si{sub 3} alloy is a unique amorphous structure in Fe{sub 90−x}Zr{sub 10}Si{sub x} ribbons. The peak temperatures of the two crystallization stages were 464 and 600 {sup ∘}C. The saturation magnetization (M{sub s}) values of the alloys ranged from 91.2 to 132.3 emu/g, and all had an initial increase before decreasing and their coercivity (H{sub c}) values increased with increased Si content. The Fe{sub 87}Zr{sub 10}Si{sub 3} amorphous alloy exhibited a low H{sub c} value of approximately 39.1 A/m, which shows good magnetic properties in the as-quenched state. After annealing, the M{sub s} of the amorphous sample considerably improved, particularly reaching 165.3 emu/g at 600 {sup ∘}C.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Fluorine-ion-beam modification of magnetic properties of thin GaMnAs films
Magnetic and electrical transport properties of fluorine-ion-beam irradiated GaMnAs films were studied as a function of ion fluence and energy of impinging ions. The different nature of defects created by ions of low- and high-energies is explored in this work by means of transport and magnetization measurements. Our results show that the saturation magnetization of the irradiated samples is suppressed as the ion fluence is increased. Interestingly, however, the same effect is not observed in the case of critical temperature, which remains nearly the same for irradiated and non-irradiated samples measured by superconducting quantum interference device. Magnetotransport measurements appear to provide more reliable results regarding the critical temperature, since they are consistent with the ion-irradiation-induced disorder in the GaMnAs film, quantified here as the increase of the resistivity. We discuss this behavior based on the inhomogeneity of damages caused by the irradiation process.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
One-step hydrothermal synthesis, characterization and magnetic properties of orthorhombic PrCrO{sub 3} cubic particles
Highlights: • Orthorhombic PrCrO{sub 3} cubic particles were prepared by a simple and facile one-step hydrothermal method. • The possible formation mechanism of PrCrO{sub 3} cubic particles was proposed. • The as-synthesized PrCrO{sub 3} exhibited behaviors of magnetic transition and negative magnetization. - Abstract: Orthorhombic PrCrO{sub 3} cubic particles were synthesized by a simple and facile one-step hydrothermal method of processing temperature 280 °C for 7 days. The products prepared in this paper have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM). The magnetic properties of the final sample are also studied. The XRD pattern shows the pure orthorhombic phase for PrCrO{sub 3} particles, the XPS and FTIR results further demonstrate the purity and composition of the product. FESEM images show cubic morphology for the PrCrO{sub 3} particles. The possible growth mechanism for PrCrO{sub 3} cubic particles is proposed. Through the investigation of magnetic properties, it can be seen that the orthorhombic PrCrO{sub 3} cubic particles exhibit behaviors of magnetic transition and negative magnetization. The Néel temperature is about 232 K and the magnetic hysteresis loop under 4 K shows that the coercivity (H{sub C}) and remanence (M{sub r}) is about 1728 Oe and 4.88 emu/g, respectively.
36 MATERIALS SCIENCE↗
Impact of Isotropic Strain on Magnetic Properties of Monolayer MoSe{sub 2}-Doped with Nonmagnetic Metal and Nonmetal Atoms
Electronic and magnetic properties of MoSe{sub 2} monolayer doped with different nonmagnetic metal (Ag, Al, Li, Mg, and Na) and nonmetal (B, C, F, N, and O) elements have been studied by using the density functional theory calculations. Magnetism has been induced by Ag, Al, and Mg doping. Then, we further have studied the effect of strain on the magnetism in Al-doped MoSe{sub 2} monolayer. We have applied an isotropic strain on the system. On the one hand, the magnetism disappeared while the compressive strain was applied. On the other hand, the magnetism kept stable under the tensile strain. Moreover, we investigated the magnetic coupling in two-Al-doped MoSe{sub 2} structures under the tensile strain. Interestingly, a tunable magnetic coupling was observed. As the tensile strain increased, the magnetic coupling between two Al atoms switched from nonmagnetic (NM) to ferromagnetic (FM). The analysis of the PDOS showed that the p-p hybridization between the Al atom and its neighboring Se atoms resulted in such magnetic behavior. Our results showed some potential applications in MoSe{sub 2}-based nanoscale devices.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Structural, morphological, optical and magnetic properties of Ag3(2+x)InxNb4-xO11+δ (0.25 ≤ x ≤ 1.0) nanoparticles synthesized by sol–gel method
Highlights: • Novel Ag{sub 3 (2+x)} In{sub x}Nb{sub 4-x}O{sub 11+δ} nanoparticles were synthesized by sol-gel method and studied their optical magnetic properties. • XRD studies confirm the single-phase monoclinic lattice structure with P2/m space group. • Morphology, purity and homogeneity of samples were confirmed by SEM images, EDX and X-ray mapping. • The absorption spectra and tauc plots confirms the semiconductor nature of the samples. • Magnetic studies reveals the ferromagnetic behavior of the samples at room temperature. - Abstract: Herein, we report the structure, morphology, optical and magnetic properties of novel Ag{sub 3 (2+x)} In{sub x}Nb{sub 4-x}O{sub 11+δ} (0.25 ≤ × ≤ 1.0; A1–A4) nanoparticles prepared by sol-gel technique. The samples were studied using X-ray diffraction, electron microscopy, diffuse reflectance spectroscopy, vibrating sample magnetometer, and electron spin resonance. X-ray diffraction studies confirm the formation of monoclinic lattice type with P2/m space group. Purity and homogeneity of the samples were confirmed by X-ray mapping. The semiconductor nature of the samples was identified by optical absorption spectra which indicate an inter-band transition from the oxygen 2p to niobium 4d electronic states. The magnetization plots reveal the room temperature ferromagnetic behavior of the samples.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Electronic Structure and Magnetic Properties of V-Monodoped and (V, Al)-Codoped 4H-SiC
Electronic structure and magnetic properties of vanadium (V)-doped 4H-SiC are researched by using the first-principle plane wave pseudopotential method based on density functional theory. Ten kinds of doping position are calculated and the most stable configuration is found. The results indicate that V-monodoped 4H-SiC favors a spin-polarized state and the magnetic moment mainly comes from the unpaired 3d electronic of V atoms. Several doping configurations studied suggest the existence of ferromagnetic coupling between V dopant. Ferromagnetic order is activated by V doping via a V{sub 0}:3d-C:2p-V{sub 7}:3d coupling chain. Hybridization occurs between p − d orbitals. The doped V atom will induce additional holes carrier into the 4H-SiC. Al itself has no contribution to the magnetic moment, whereas V- and Al-codoped 4H-SiC can induce spin polarization, which reveals that the FM stability is reduced significantly by Al codoping. The calculated electronic structure implies that the presence of Si vacancies (V{sub si}) weakens the FM state of V- and V{sub si}-codoped 4H-SiC.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Electronic and magnetic properties of TTF and TCNQ covered Co thin films
Interfacial effects like orbital hybridization and charge transfer strongly influence the transfer of spins from ferromagnetic metals to organic semiconductors and can lead to the formation of interfacial states with distinct magnetic properties. The changes in the electronic and magnetic properties of a thin Co film upon adsorption of a layer of either the molecular organic electron donor tetrathiafulvalene (TTF) or the acceptor tetracyanoquinodimethane (TCNQ) have been investigated by X-ray absorption spectroscopy and X-ray magnetic circular dichroism using synchrotron radiation. Clear differences between the spectra of the adsorbed molecules and the neutral molecules show the hybridization of the molecular orbitals with the Co interface. Deposition of both organic materials leads to a small increase of the ratio of the orbital magnetic moment to the spin magnetic moment of the Co atoms at the interface. The main effect of overlayer deposition is a modification of the magnetic hysteresis of the Co film: The TCNQ slightly reduces the coercivity of the Co, while the TTF increases the coercivity by a factor of ∼1.5. These complementary effects of either a molecular organic electron donor or acceptor on the interfacial properties of a metal ferromagnetic thin film are a promising result for the controlled modification of the magnetic structure of hybrid interfaces.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗