Magnetic properties of the intermetallic compounds Y15Fe77−xTxB8 (T = Mn,Co, Ni,x = 7, 17)

Magnetic properties of the compounds Y₁₅Fe_77−xT_xB₈, where T stands for Mn, Co or Ni and x equals 7 or 17 were investigated within the temperature range 80 to 650 K. X-ray diffraction yielded a tetragonal structure of Nd₂Fe₁₄B type for all samples. The compounds appeared ferromagnetic: substitution of Mn or Ni for Fe leads to decrease of the Curie temperature and magnetization, while an increase of both quantities was observed for T = Co.     

Magnetic behaviour of U(MnxAl1−x)2 compounds

The results of magnetic measurements performed on U(Mn_xAl_1−x)₂ compounds in the temperature range 4.2K < T < 800K are reported. In the low temperature range (T < 200K), UMn₂ shows a Pauli-type paramagnetism. Above 420K a Curie-Weiss behaviour is evidenced. The magnetic properties of U(Mn_xAl_1−x)₂ compounds were analysed assuming a superposition of a temperature dependent term on a Pauli-type contribution, χ_O. The effective moments as well as the χ_O values were determined both in the low (T < 200K) and high (T > 420K) temperature range. The experimental data were discussed considering changes in the band structure and/or quenching of spin fluctuations.     

Magnetic resonance in a gallium-doped Cu–Cr–S structure

A layered Cu–Cr–S structure doped with Ga ions and consisting of single-crystal CuCrS₂ layers, embedded with thin plates of spinel phases CuCr₂S₄ and CuGa_xCr_2–xS₄, has been studied using the magnetic resonance and magnetic susceptibility methods. The Curie temperature and the saturation magnetization of the spinel phases of the samples have been determined. The spinel phase layer thickness has been estimated.     

Magnetic and electric properties of Yb x Mn1 − x S alloys

Results from investigating the structural, magnetic, and electrical properties of Yb _x Mn_{1 ? x} S alloys (0 ≤ x ≤ 0.2) synthesized on the basis of manganese monosulfide are presented. Substituting manganese for ytterbium increases the concentration of charge carriers and lowers the activation energy. The observed anomalies in the temperature dependence of resistivity are explained by an impurity semiconductor model with donor 4f levels.     

Magnetic,electronic and electron spin resonance studies of the (Gd1−xYx)Ni2 compounds

Magnetization, electron spin resonance and heat capacity measurements have been made on the (Gd_1-xYx)Ni₂ compounds. Magnetization measurements reveal a moment deficiency for gadolinium in this series. In GdNi₂ a value of 6.92μ_B is obtained for the gadolinium moment, which decreases further with yttrium substitution. In the concentration range 0.2 ⩽ x ⩽ 0.8 the samples show features seen in inhomogeneous ferromagnets.The ESR measurements reveal a negative g-shift and a very shallow ESR bottleneck in this system.The specific heat of the samples in the concentration range 0.2 ⩽ x ⩽ 0.8 show complex behaviour: downturn at low temperatures in the usual (C/T) against T² graphs, anomalously large γ-values and so on. In the remaining compounds the specific heat shows normal behaviour. At the YNi₂ end of the series a rapid increase in the host density of state takes place when gadolinium is substituted for yttrium.     

Magnetic properties, magnetoresistance, and Raman spectra of CuV x Cr1 − x S2

The results of investigations of the magnetic and Raman spectra, magnetic properties, and magnetoresistance of vanadium-substituted chromium copper disulfides CuV _x Cr_{1 ? x} S₂ (x = 0.1) are presented.     

Magnetic properties of RNi1−xIn1+x (R=Gd–Er) compounds

AC and DC bulk magnetic measurements were performed for RNi_1−xIn_1+x (R=Gd–Er and x=0,0.1, 0.25) compounds. These compounds crystallize in the hexagonal ZrNiAl-type structure. The lattice parameters a and c for the RNiIn series decrease linearly with increasing number of 4f electrons. For nonstoichiometric RNi_1−xIn_1+x additional indium atoms occupy the 2(c) crystallographic site and the a parameter increases while the c parameter decreases with increasing indium content. The stoichiometric samples show ferromagnetic behavior with the critical temperature changing from 96 K for R=Gd to 9 K for R=Er. In the nonstoichiometric RNi_1−xIn_1+x compounds increase in the indium content leads to decrease in the ferromagnetic critical temperatures and to a change of the antiferromagnetic ordering for x=0.25 in the case of R=Dy, Ho and Er.     

Quantum-chemical modeling of the electronic structure and magnetic properties of Sn1 − x − y M x Sb y O2, M = Cr, Mn, Co, or Ni (x = 0.25; y = 0, 0.25)

The electronic and magnetic structures of the Sn_0.75 M _0.25O₂ and Sn_0.5 M _0.25Sb_0.25O₂ (M = Cr, Mn, Co, Ni) compounds with a structure that is derivative of the rutile structure are modeled using the ab initio spin-polarized tight-binding linear muffin-tin orbital (TB-LMTO) method. The magnetic moments of the transition metal atoms are calculated. The data obtained are used to analyze the influence of the composition of Sn_{1 ? x ? y} M _x Sb _y O₂ phases on their electronic spectra and the magnetic and transport characteristics.     

Giant magnetoresistance of MexMn1−x S (Me=Fe, Cr) sulfides

The structural, electrical, and magnetic properties, as well as the magnetoresistance of polycrystalline Me_xMn_1?x S (Me=Fe and Cr) sulfides were investigated in longitudinal magnetic fields of up to 50 kOe over the temperature range 4.2–300 K. The ferromagnetic compound Fe_xMn_1?x S (x=0.29) exhibits the giant magnetoresistance (GMR) effect with magnitude δ_H=?450% in a field of 30 kOe at 50 K. Antiferromagnetic Cr_xMn_1?x S (x=0.5) sulfide undergoes a transition to the GMR state δ_H～?25% in a field of 30 kOe at 4.2 K) in the region of antiferromagnet-ferromagnet transition (T _c ～66 K). A mechanism of the GMR in these compounds is discussed.     

Magnetic microstructure of strontium-substituted thulium ferromanganites Tm0.65Sr0.35Mn1 ? x Fe x O3 (x = 0.3?0.4)

The structural and magnetic properties of the Tm_0.65Sr_0.35Mn_{1 ? x} Fe _x O₃ (x = 0.3?0.4) have been studied by methods of magnetic resonance and differential thermomagnetic analysis. A magnetic phase separation has been revealed in structurally single-phase samples.     

Magnetic structures of non-stoichiometric hexagonal RNi1−xIn1+x (R=Dy,Ho, Er) compounds

Results of neutron diffraction studies of DyNi_0.9In_1.1, HoNi_0.8In_1.2 and ErNi_0.9In_1.1 compounds crystallizing in the hexagonal ZrNiAl-type structure are reported. Previously published data for stoichiometric 1–1–1 compounds indicate that HoNiIn and ErNiIn compounds are ferromagnets (ordering along the c-axis) with T_C of 22 and 9 K, respectively, while DyNiIn was found to be an antiferromagnet with T_N of 32 K (J. Magn. Magn. Mater. 262 (2003) L177; J. Magn. Magn. Mater., in press). DC bulk magnetic measurements show that with the rise of the x parameter the ordering temperature is lowered; moreover changes in the magnetic ordering occur. At 1.5 K the HoNi_0.8In_1.2 compound has a non-collinear magnetic structure, for the ErNi_0.9In_1.1 compound an additional sine-modulated component lying in the basal plane was found. For the DyNi_0.9In_1.1 compound the antiferromagnetic character of magnetic coupling is conserved, but some changes in comparison to 1–1–1 stoichiometry were noticed.     

Magnetic and dynamic properties of Sm x Mn1 − x S solid solutions

The real and imaginary parts of the magnetic permeability at frequencies of 0.1, 1.0, and 10.0 kHz, as well as the electron paramagnetic resonance (EPR) line width and g-factor, have been measured in Sm _x Mn_{1 ? x} S (0.10 < x < 0.25) solid solutions in the temperature range 5–300 K. The logarithmic dependence of the maximum in the imaginary part of the magnetic permeability on the frequency and the power-law dependence of Imμ on the temperature have been determined. The mechanism of relaxation of the magnetic moment in the magnetically ordered and paramagnetic phases has been established. The experimental results have been explained in terms of the Heisenberg model with competing exchange interactions and the formation of the antiaspiromagnetic state at low temperatures.     

Magnetic properties of (Mn1 − x Fe x )1.68Sn solid solutions

Solid solutions in the (Mn_{1 ? x} Fe _x )_1.68Sn system (x ≤ 0.5) with a Ni₂In-type structure are synthesized by the solid-phase reaction method in a stepwise temperature regime. The unit cell parameters a and c decrease with an increase in the iron concentration in the alloys and become equal to a = 0.430 nm and c = 0.538 nm for the (Mn_0.5Fe_0.5)_1.68Sn alloy. A superstructure with the unit cell parameters a _ss = 3a and c _ss = c is revealed in alloys of the system under investigation. The specific magnetization of the alloys increases nonlinearly from 53 G cm³ g^?1 in the Mn_1.68Sn alloy to 72 G cm³ g^?1 in the (Mn_0.5Fe_0.5)_1.68Sn solid solution. The Curie temperature changes from 270 K in the initial alloy of the composition Mn_1.68Sn to 365 K in the alloy of the composition (Mn_0.5Fe_0.5)_1.68Sn. All solid solutions in the (Mn_{1 ? x} Fe _x )_1.68Sn (x ≤ 0.5) system exhibit metallic conductivity in the temperature range from 77 to 450 K.     

Superconducting and electronic properties of the metallic glass system La75Si25−x M x (M=Cr,Mn, Fe,Co, Ni,Cu, B,Al, Ga,In)

A new ternary metallic glass system, La₇₅Si_25–x M _x (where M is a 3d or a IIIA element) has been prepared by melt spinning. The superconducting transition temperature,T _c , is depressed by the magnetic 3d elements. For low Fe concentrations (less than 5 at.%) the depression is about 0.3 K/at.%. Part of the depression may be explained by a decreased density of states atE _F as determined by UPS measurements. The strongest depression is associated with the magnetic pair breaking due to spin scattering. In the IIIA additions we correlateT _c with the atomic radius of the additive.     

Magnetic properties in the series TlxV6−yMyS8 (M = Cr,Mn, Fe;0 ⩽ y ⩽ 1)

Ternary vanadium sulfides with various 3d transition metal substitutes were prepared by thermal treatment and characterized by X-ray diffraction. Magnetic susceptibility measurements on the homogeneous powders reveal that itinerant and localized magnetism in all samples coexists, due to different ionic charges. The localized magnetic behaviour increases in the direction of the late 3d elements. With Mössbauer spectroscopy a Fe²⁺ in the high spin state is found. The magnetic behaviour of the series will be discussed.     

Pressure Dependence on the Magnetic Structures of TbNi 1−x Cu x ( x =0.3 & 0.4) Using Neutron Techniques

In the TbNi 1 m x Cu x series, the Cu substitution has two main effects: the increase of the cell volume (～4.3% from TbNi to TbCu), and the increasing importance of antiferromagnetic interactions. In this sense, the magnetic structures of these compounds evolve from a non-collinear ferromagnetic (FM) arrangement to an incommensurate antiferromagnetic (AFM) one for Cu concentration larger than 35%. In this paper, we present the effects of pressure on the magnetic structures of the compounds which are closer to this critical concentration: TbNi 0.7 Cu 0.3 (FM) and TbNi 0.6 Cu 0.4 (AFM). It appears that a global antiferromagnetic behaviour is favoured by pressure.     

Electron work function of LaNi5 ? x T x (T = Al, Cu, Fe; x = 0, 1) intermetallics

The method of contact potential difference is applied to determine the electron work function of ingots and pellets (compacted powder) of LaNi_{5 ? x} T _x (T = Al, Cu, Fe; x = 0, 1) intermetallics at 293 K. A correlation is revealed between the electron work function and the heats of formation of the intermetallics and their hydrides.     

Magnetic properties of (GdxY1−x)Co2B2 compounds

Magnetic measurements were performed on the (Gd_xY_1−x)Co₂B₂ compounds, in the temperature range 2–800 K and fields up to 70 kOe. YCo₂B₂ is a paramagnet. The (Gd_xY_1−x)Co₂B₂ compounds with x≥0.2 shows a ferromagnetic type ordering. The saturation magnetization at 2 K coincides only with the contribution of gadolinium. The Curie temperatures are nearly linearly dependent on the composition. Above the Curie points, the thermal variations of the magnetic susceptibility can be described as a superposition of a temperature independent term ϰ₀ on a Curie-Weiss behavior. The Curie constants are determined by the contribution of Gd³⁺ ions only. The ϰ₀ values increase when the gadolinium content is greater. The observed properties are discussed in the wider framework of the magnetic behavior of cobalt in GdCo_xB_y compounds.     

Structural features of the system of cubic crystals Zn0.999Fe0.001S1 ? x Se x (x = 0, 0.2)

The structural state of cubic single crystals Zn_0.999Fe_0.001S_{1 ? x} Se _x (x = 0, 0.2) obtained by the chemical transport method has been investigated using thermal neutron diffraction for the first time. It has been found that the diffraction patterns of these crystals contain the previously unknown effects of diffuse scattering caused by local statistic atomic displacements in the metastable fcc lattice.     

Magnetic Parameters of Hg1–x Mn x Se1–y S y and Hg1–x Mn x Te1–y S y Crystals

The magnetic susceptibility of Hg_1–x Mn _x Se_1–y S _y and Hg_1–x Mn _x Te_1–y S _y crystals is investigated by the Faraday method at H = 3 kOe in the temperature interval T = 77–300 K. It is established that the specific features of are due to Mn–S–Mn–S, Mn–Se–Mn–Se, and Mn–Te–Mn–Te clusters and mixed Mn–Se–Mn–S and Mn–Te–Mn–S clusters of different sizes in which the indirect exchange antiferromagnetic interaction between Mn atoms is realized through chalcogen atoms. Based on the dependences 1/_Mn = f(T), the magnetic parameters are determined and their dependences on the crystal composition (x and y) are established.