Magnetic and electrical properties of the UCu2T3Al7 alloys

The UCu₂T₃Al₇-type compounds with T = Cr, Mn and Fe crystallize in the tetragonal ThMn₁₂-type structure (I4/mmm space group). Magnetic properties have been examined in magnetic fields up to 50 kOe in the temperature range 1.9–400 K using a SQUID magnetometer. The Cr based pseudoternary alloy is paramagnetic with the linear field dependence of the magnetization at 1.9 K. The temperature dependence of the magnetic susceptibility is described by a modified Curie–Weiss (MCW) law. The Mn containing compound is ferrimagnetic and the field dependence of the magnetization does not reach saturation while the magnetic susceptibility follows the MCW law at high temperature. The Fe alloy is ferromagnetic and at higher temperature the MCW law is fulfilled. The temperature dependence of the electrical resistivity of all materials was examined between 4.2 and 300 K showing metallic character. The Mn and Fe based compounds demonstrate some anomalies in the ρ(T) plot at low temperature. The results are discussed in relation to the anomalies observed in magnetic measurements.     

Law of approach to saturation in highly anisotropic ferromagnets Application to Nd---Fe---B melt-spun ribbons

The magnetization curves of melt-spun ribbons of Nd---Fe---B with (BH)_max=16 MGOe have been measured in pulsed high magnetic fields up to 400 kOe to examine the applicability of the law of approach to ferromagnetic saturation to highly anisotropic uniaxial ferromagnets. The magnetization in the region M≥0.95 Ms can be described well with the law of approach to saturation. From the analysis of the magnetization curve, the spontaneous magnetization, effective anisotropy constant and high-field susceptibility are estimated at room temperature. These values are consistent with those evaluated from single-crystalline data of Nd₂Fe₁₄B.     

Thermodynamics of a helicoidal magnetic structure in a spin-wave approximation

Specific features of the heat capacity, magnetization, and magnetic susceptibility of a chiral magnet caused by the magnon contribution have been studied. It has been shown that the local heat capacity and the magnetization are functions of the coordinates and that their behavior depends on the magnitude of an applied magnetic field. The temperature dependences of these quantities have been investigated. The results of the approximate analytical calculations and numerical calculations have been compared between themselves.     

Magnetic properties and structure of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi<Subscript>2</Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 1.5)

Crystal structure, magnetization, coercive force, magnetic susceptibility, and anisotropic magnetostriction of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi₂Mn _x (0 ≤ x ≤ 1.5) have been studied. The samples with x ≤ 1 have an fcc structure, whereas TbNi₂Mn_1.25 has a rhombohedral structure of the PuNi₃ type. It has been found that the magnetic ordering temperature increases sharply when manganese is added. As the Mn concentration grows, the magnetization and the magnetostriction decrease monotonically, while the coercive force increases. The experimental data obtained have been interpreted on the assumption that a partial substitution of manganese for terbium in TbNi₂Mn _x leads to local distortions of the crystal field acting on Tb ions, to the appearance of a local uniaxial random anisotropy, and to the formation of a noncollinear magnetic structure in the terbium sublattice.     

Crystal structure and magnetic properties of pseudobinary solid solutions Pr(In1 − x Pb x )3

Structure and magnetic properties of Pr(In_{1 ? x} Pb _x )₃ alloys have been studied in some detail. It has been shown that, in this system, in the whole range of compositions (0 ≤ x ≤ 1), there is a continuous series of disordered solid solutions with a structure of the Cu₃Au type. The lattice parameter of these solid solutions varies linearly (according to Vegard’s law). The temperature dependence of the magnetic susceptibility has been studied in the temperature range of 2–300 K. At enhanced temperatures, it is described well by the Curie-Weiss law for all alloys. At low temperatures, an anomalous deviation from this law for the terminal alloys is observed, which is especially strong for PrIn₃. In pseudobinary alloys, this anomaly weakens and the magnetic susceptibility itself increases. In the concentration dependence of the susceptibility measured at 2 K, a maximum is observed. The specific features of the dependence of the magnetic susceptibility of pseudobinary alloys on the temperature and concentration x have been explained by a decrease in the local symmetry of crystal field at the sites of Pr³⁺ ions due to the partial random replacement of their nearest neighbors by atoms of different valences.     

Magnetic and transport properties of YbRhIn and YbPdIn

Electrical resistivity, magnetization and specific heat have been measured on a single crystal of YbRhIn and polycrystals of LuRhIn and YbPdIn. It is confirmed that YbPdIn is a metal with a divalent Yb ion. For YbRhIn, the electrical resistivity increases with logarithmic temperature dependence with decreasing temperature and saturates at a constant value below 20 K, while that of the nonmagnetic reference LuRhIn shows typical metallic behavior. The magnetic susceptibility of YbRhIn indicates that the Yb ion is in the trivalent state. The irreversibility of the magnetization curves which is observed in the high pulsed magnetic field below 1.5 K suggests an increase of relaxation time in the magnetic system. The specific heat increases rapidly below 4 K with decreasing temperature down to 0.9 K and moves toward higher temperatures on application of a magnetic field. These facts suggest that some magnetic transition to either ferromagnetic or spin-glass state occurs at low temperature.     

MAGNETIC PHASE DIAGRAM OF SmMn_2(Ge_(1-x)Si_x)_2 SYSTEM

1.IntroductionTheternaryRMn2X2compounds(Risrareearth,andXisGeorSi)crystallizeinthebodycenteredtetrag0nalThCr2Si2-typestructurewithspacegr0upI4/mmm,inwhichtheR,TandXatomsoccuPythe2a,4dand4csites,respectivelyl1t2].Theyexhibitillterestingmagneticpr0perties['].InSmMn2Ge2tlireedifferentmagneticorderingtypeshavebeendetermined:ferromagnetismfor153K相似文献   

纳米Fe-ZnSe颗粒膜的结构与磁性

采用射频溅射法制备了纳米铁磁金属-半导体基体Fe0.35(ZnSe)0.65颗粒膜,并研究了其结构和磁特性.根据颗粒膜低场磁化率x(T)温度关系和不同温度下的磁滞回线,证实了在一定的温度范围内,颗粒膜中的纳米铁颗粒表现出磁性弛豫效应.当截止温度TB=50 K时.颗粒膜的磁性由超顺磁性转变为铁磁性.在截止温度以上,其饱和磁化强度Ms(T)温度关系符合Bloch的自旋波T3/2定律,探讨分析了自旋波常数增大的原因.     

Magnetocrystalline anisotropy and exchange interactions in the novel R3(Fe, V)29 compounds (R = Y, Nd, Sm)

A type of magnetocrystalline anisotropy and exchange interactions of the novel ternary R₃(Fe, V)₂₉ compounds (R = Y, Nd, Sm) have been investigated. The compounds are uniaxial ferromagnets with easy magnetization direction along the [ 0 1] axis of the monoclinic lattice at room temperature. The temperature variations of the magnetic moment and the first anisotropy constant for Y₃(Fe, V)₂₉ are presented. The first order magnetization process along the hard magnetization direction takes place for Sm₃(Fe, V)₂₉ at T < 120 K. A magnetic anomaly is detected in the temperature dependence of the a.c. susceptibility for Nd₃(Fe, V)₂₉ which can be related to a spin reorientation.     

Temperature dependence of magnetic properties of a disordered Fe<Subscript>0.65</Subscript>Ni<Subscript>0.35</Subscript>

The method of calculation of average and local magnetic characteristics of transition metals at finite temperatures developed by the author and Grebennikov in previous works and based on the employment of a real band structure and spin fluctuations has been applied to a disordered invar alloy Fe_0.65Ni_0.35. The magnetization, Curie temperature, local magnetic moment, and uniform and local susceptibilities have been calculated for both ferromagnetic and paramagnetic states. The results are in agreement with experimental data in a wide temperature range. It has been shown that the effect of disorder in the filling of sites with Fe and Ni atoms on the magnetic properties of the Fe-Ni invar is insignificant.     

Magnetic anisotropy of the Nd<Subscript>2</Subscript>Fe<Subscript>14</Subscript>B compound and its hydride Nd<Subscript>2</Subscript>Fe<Subscript>14</Subscript>BH<Subscript>4</Subscript>

Magnetization curves of single crystals of Nd₂Fe₁₄B and its hydride Nd₂Fe₁₄BH₄ have been measured along their principal crystallographic directions in a temperature range of 4.2–280 K. The magnetic anisotropy constants, which allow one to describe experimental magnetization curves as well as the low-temperature “easy-cone”-type magnetic structure and field-induced first-order magnetic phase transitions, have been determined in terms of a collinear-ferrimagnetic-ordering model. The anisotropy constants were shown to decrease in magnitude upon hydrogenation. In this case, the ratios of the effective fourth-and sixth-order constants to the second-order constant increase, whereas the constants responsible for the basal-plane anisotropy exhibit a more than threefold decrease. At the same time, the spin-reorientation temperature and opening of the magnetization cone at 4.2 K remain virtually unchanged. The results obtained are discussed in terms of the single-ion-anisotropy theory.     

TbMn6—xCoxSn6赝三元化合物的结构和磁性

本文研究了ＴｂＭｎ６－ｘＣｏｘＳｎ和赝三元化合物的结构和磁性，结果表明：用Ｃｏ部分取代ＴｂＭｎ６Ｓｎ６中的Ｍｎ不改变其晶体结构，但随Ｃｏ含量的增加晶格常数和单胞体积单调减小；居里温度随Ｃｏ含昨增大而降低；自旋重取向温度也随Ｃｏ含量增大而降低，但Ｃｏ含≥０．６时自旋重取向消失；     

Magnetic phase transitions in ferrimagnetic DyFe5Al7 near the compensation point

The magnetization curves of single-crystal DyFe₅Al₇ have been measured along the main crystal-lographic directions in the magnetically ordered state. The temperature dependences of the magnetic moments of the Dy and Fe sublattices and the parameter of the intersublattice exchange have been determined in the model of molecular field. Upon the measurements along the easy axis, jumps of magnetization, the values and critical fields of which strongly depend on temperature, have been revealed near the temperature of magnetic compensation. A model of the magnetization of a ferrimagnet with two magnetic sublattices coupled by weak intersublattice exchange has been suggested. Using this model, analytical expressions for the magnetization curve and critical field of the spin-reorientation transition have been obtained. A magnetic phase diagram has been constructed and magnetic structures that are realized in different fields at different temperatures have been determined. The generalization of the model to the case of a noncollinear Fe sublattice has been generalized.     

Magnetic investigations in liquid Al–In

Measurements of the magnetic susceptibility in liquid alloys of indium with 0–20 at% aluminium are reported. Within the investigated range of temperature and composition all alloys are found to be diamagnetic. The increase of the magnetic susceptibilty due to the addition of aluminium follows a simple linear mixing law. The departures from the free electron behavior are analyzed in terms of the interactions between the electrons and the ion cores and the effect of exchange-correlation between the electrons. The potentials of the cores are indicated to have a very small influence on the electronic part of the susceptibility whereas electronic exchange-correlation yields enhancements of 20% at all compositions. The ambiguity due to the divergent estimates for the contributions of the diamagnetic cores to the total susceptibility is briefly discusssed.     

Structure and magnetic properties of Pr0. 1CexTb0.9-xFe1.9 alloys

1　INTRODUCTIONTerfenol D ( Tb0.27 Dy0.73 Fe2 ) exhibits largemagentostriction and minimized magnetic anisotro py at room temperature[1], so it is widely used inactuators and transducers. But the main raw mate rials of Terfenol D are expensive Tb and Dy. Ac cording to the single ion model[2], CeFe2 and PrFe2compounds have larger magnetostriction thanTbFe2 and DyFe2 at 0 K. In addition, Ce and Prare much cheaper than Tb and Dy. So Ce basedand Pr based compo…     

Electronic structure and magnetism of PrNixPt1−x compounds

We have studied influence of the Pt–Ni substitution on the crystal structure and magnetic behavior of the PrNi_xPt_1−x compounds. Polycrystalline samples with x = 1, 0.9, 0.75, 0 were prepared and characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). The analysis of XRPD data confirmed that the orthorhombic CrB-type structure owned by the parent binary compounds remains conserved through the entire series. The samples were subsequently investigated by specific heat (C_p), magnetization (M) and ac susceptibility measurements in the temperature range 2–350 K and in magnetic fields up to 9 T. All compounds were found to order ferromagnetically. The T_C values monotonously increase with increasing Ni content. To inspect the crystal-field (CEF) effects and magnetocaloric properties specific-heat data were analyzed in detail and the magnetic contribution to the specific heat together with the magnetic entropy have been determined. The results of first principles electronic structure calculations of the PrNi and PrPt confirmed that besides the stable Pr magnetic moments due to localized 4f-electrons only a very small magnetic moments of at most 0.2μ_B is induced at the Ni (Pt) site due to the polarized 3d-electron states (5d-electron states) hybridizing with the Pr 5d-electron states, i.e. the Ni (Pt) moment plays only minor role in the total balance of the magnetic moments in these compounds.     

内扩散法Nb3Sn多芯线材的磁化特性研究

研究了内扩散法Ｎｂ３Ｓｎ多芯线材随温度和磁场变化的磁化曲线及磁化率,绘出了磁化量－磁场－温度（Ｍ－Ｈ－Ｔ）的三维临界曲面,归一化后的磁化曲线基本符合Ｋｒａｍｅｒ拟和方程。计算得到的Ｎｂ３Ｓｎ多芯线材有效直径比芯线的原始几何尺寸要大,其原因在于微观结构中存在着“桥梁”,分析表明,多余的磁滞损耗来自于“桥梁”。交流磁化率和Ｘ’和Ｘ″在给定频率和背景磁场下,随交流振幅的变化很小,在给定交流振幅下,随交流     

Effect of a nanosized state on the magnetic properties of Ni3(Al,Fe) and Ni3(Al,Co)

An analysis of the magnetic properties of the binary Ni₃Al intermetallic compound (unalloyed and alloyed with iron and cobalt) after high-pressure torsion has been carried out. For all of the alloys studied, the deformation using ten revolutions of the anvils at 10 GPa results in the formation of a nanocrystalline condition. After the deformation, a significant decrease takes place in both the magnetic susceptibility of the Ni₃Al alloy and magnetization of the Ni₃Al-Co intermetallic compound. The initially ferromagnetic Ni₃Al-Fe alloy becomes paramagnetic at room temperature.     

Dynamic magnetic properties of ZnO nanocrystals incorporating Fe

The aim of the present work is to study the magnetic properties of ZnO(Fe) nanocrystalline samples prepared by two methods of synthesis. We have used the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The dynamic magnetic properties were studied by means of AC susceptibility χ. The measurements were performed at small AC magnetic field with amplitude not exceeding 5 Oe and different frequency values (from 7 Hz to 9970 Hz). The AC susceptibility maxima have been found for in-phase susceptibility Re(χ) and for out of phase susceptibility Im(χ). We analyzed the observed frequency dependence of the peak temperature in the AC susceptibility curve using the empirical parameter Φ that is a quantitative measure of the frequency shift and is given by the relative shift of the peak temperature per decade shift in frequency, as well as Vogel-Fulcher law.     

Magnetic properties of <Emphasis Type="Italic">R</Emphasis>Co<Subscript>2</Subscript> compounds in the exchange-striction model of ferrimagnets

The original version of the exchange-striction model of a ferrimagnet has been employed for calculating a number of magnetic properties of RCo₂ ferrimagnets, where R = Er, Ho, Dy, Tb, and Gd are rareearth ions. The following magnetic properties are calculated: pressure dependence of the Curie temperature (Т _С), temperature dependences of magnetization in sublattices of cobalt and rare-earth atoms, and isotherms of magnetization of these lattices at Т > Т _С. For an ErСо₂ sample, the Н–Т phase diagram has been constructed and the magnetization in the magnetic fields Н = 0–70 Т has been calculated. The calculated and experimental results have been compared. Based on the exchange-striction model, the qualitative explanation of the difference in the type of the magnetic phase transformation in the intermetallic compounds with R = Tb and Gd and R = Er, Ho, and Dy is given.