Magnetic anisotropy and spin-reorientation in HoAl2

Torque measurements have been performed at several temperatures and magnetic fields, on a single crystal of HoAl₂ in the (1 1 0) plane. The easy magnetization direction changes from the [1 0 0] to [1 1 0] near T_R = 20 K in magnetic fields between 0.2 and 1.6 T. At temperatures below T_R a new non-major cubic symmetry easy direction appears which rotates with temperature in the plane of the sample. This behaviour and that of the complete torque curves have been interpreted on the basis of a single ion model.     

Magnetic excitations of HoAl2 in a magnetic field

The ground state spin wave excitation energies of single crystalline HoAl₂ have been studied at T= 4.2 K in external magnetic fields up to 7 T by means of inelastic neutron scattering. The results have been interpreted in terms of a cubic crystalline electric field using the parameters determined by magnetization measurements and an exchange interaction with the exchange parameters taken from the zero field measurements.     

Magnetic properties of A DyNi2 single crystal

Magnetic measurements have been performed on a single crystal of DyNi₂ in applied fields up to 135 kOe. In the ferromagnetic range (T_c = 25 K), the easy magnetization direction is [100] and the hardest one is [111]. Crystal field parameters have been determined from the field and temperature dependence of the magnetization measured along the three principal axes. A two-dimensional model has been used to take into account the rotation of magnetization towards the field. The deduced parameters are W = -0.8 K and x = 0.49. The corresponding anisotropy is very large: especially even a field of 135 kOe applied along a difficult magnetization axis cannot rotate the magnetization along this direction.     

Magnetic properties of Y2Fe15Cr2 single crystal

A Y₂Fe₁₅Cr₂ single crystal with the Th₂Ni₁₇-type structure has been prepared by the Czochralski method and investigated by means of Laue back-reflection, metallographic observation, X-ray diffraction, the singular point detection technique and magnetic measurements. A magnetohistory effect has been observed at a low temperature. Magnetization curves have been measured along the easy and hard directions in fields up to 6.5 T. The saturation magnetization and magnetocrystalline anisotropy field decrease with increasing temperature. The experimental magnetocrystalline anisotropy constant is in good agreement with the calculation results on first approximation.     

First order reorientation in HoAl2

Accurate torque experiments have clearly shown that the reorientation of the magnetization observed in HoAl₂ near 20 K is a first order transition. A hysteresis of almost 2 K is observed.     

Magnetic properties of CeB6 single crystal

Magnetic measurements of CeB₆ have been made in fields up to 80 kOe at temperatures up to 1000 K. Below 2.3 K, each magnetization vs field curve shows several critical points depending on the direction of field, but between 2.3 and 3 K, the curve is smooth. Above about 3 K, the magnetization curve has a break point at a certain field which increases monotonically with increasing temperature. The paramagnetic susceptibility has been analysed by assuming appropriate values of crystal-field splitting and exchange interactions. From these results, a magnetic phase diagram for CeB₆ has been proposed.     

Magnetic behavior and structural feature of quasi-one-dimensional BaCu2V2O8 crystal

Magnetic properties of BaCu₂V₂O₈ single crystals obtained by the spontaneous nucleation method using V₂O₅ as a self-flux are investigated. Singlet ground states with spin gaps of 215 and 223 K are observed along the directions parallel and perpendicular to the c-axis of the crystal, respectively, being in good agreement with powder sample measurements. Reinvestigation of the crystal structure reveals that the whole structural framework of BaCu₂V₂O₈ crystal can be described as an assembly of alternating chains, which are built by edge-sharing pairs of CuO₄ square-plaquettes and VO₄ tetrahedra along the c-axis. The magnetic nature of BaCu₂V₂O₈ is well understood based on this structural interpretation.     

Magnetic behavior of nanocrystalline LaMn2Ge2

The compound, LaMn₂Ge₂, crystallizing in ThCr₂Si₂-type tetragonal crystal structure, has been known to undergo ferromagnetic order below (T_C=) 326 K. In this article, we report the magnetic behavior of nanocrystalline form of this compound, obtained by high-energy ball milling. T_C of this compound is reduced marginally for the nanoform, whereas there is a significant reduction of the magnitude of the saturation magnetic moment with increasing milling time. The coercive field however increases with decreasing particle size. Thus, this work provides a route to tune these parameters by reducing the particle size in this ternary family.     

Magnetic phase transitions in Nd7Rh3 single crystal

Magnetic phase transitions in rare earth intermetallic compound Nd₇Rh₃ have been investigated using a single crystal. Measurement results of magnetization, magnetic susceptibility, specific heat, and electrical resistivity reveal that Nd₇Rh₃ has two magnetic phase transitions at T_N=34 K, T_t2=9.1 K and a change of the magnetic feature at T_t1=6.8 K in the absence of an external magnetic field. Antiferromagnetic orderings exist in all the three magnetic states; a large magnetic anisotropy between the c-axis and the c-plane is observed. In the magnetic phase below T_t2, an irreversible field-induced magnetic phase transition takes place in the c-plane; after removing external magnetic field, a coexistence state of ferro- and antiferromagnetic ordering or a ferrimagnetic state having a remanent magnetization M_R is stabilized. The M_R decays to a certain value for several hours after the first process; a magnetic field cooling effect was also observed in the c-plane below T_t2. In the antiferromagentic state above T_t2, the irreversibility disappears and an ordinary antiferromagnetic state takes place. As the origin of this phenomenon, a kind of martensitic structural transition that is observed in Gd₅Ge₄ can be considered.     

Magnetostriction measurements of CoS2 single crystal

The magnetorestriction constants of CoS₂ single crystal were measured by a capacitance method in a temperature range from liquid N₂ to the Curie temperatures.The constants γ₁₀₀ and γ₁₁₁ are ?1.9 × 10^?6 and 5.7 × 10^?6 at liquid N₂ temperature respectively, and the absolute values of the constants decrease monotonically with the increase of the temperature. The volume magnetorestriction constant δω/δH at 110 K in the ferromagnetic state is 6 × 10^?10 Oe^?1.     

Magnetic ordering in U4Cu4P7 single crystal

The magnetic ordering in the tetragonal ternary compound U₄Cu₄P₇ has been studied by neutron diffraction. It orders below T_N = 146 K with an antiferromagnetic structure of wave vector k = (001). The magnetic ordering corresponds to a stacking of ferromagnetic (001) uranium planes according to the sequences m₁, m₁, m₂, -m₂, -m₁, -m₁, -m₂, m₂ where m₁ and m₂ represent the magnetic moment, directed along the tetragonal axis of the two uranium sites U(1) (0,0,± z₁) and U(2) (0,0, ± z₂) respectively. The magnetic moments on these two sites have different temperature dependencies as well as well as they reach the different values of 1.1 and 2.2.μ_B for the U(1) and U(2) sites, respectively.     

Magnetic anisotropy of Sm2Fe14B single crystal

Magnetization measurements have been made on a Sm₂Fe₁₄B single crystal in magnetic fields up to 140 kOe. The easy direction of the magnetization lies along [100] in the tetragonal structure P4₂/mnm. Magnetic anisotropy energies at 290K along [110] and [001] have been estimated to be 5.8×10⁶ and 1.1×10⁸ erg/cm³, respectively, both becoming much larger at lower temperature. No evidence of the spin canting of Nd₂Fe₁₄B type is observed even at 4.2K.     

Magnetic anomalies in single crystalline ErPd2Si2

Considering certain interesting features in the previously reported ¹⁶⁶Er Mössbauer effect, and neutron diffraction data on the polycrystalline form of ErPd₂Si₂ crystallizing in the ThCr₂Si₂-type tetragonal structure, we have carried out magnetic measurements (1.8–300 K) on the single crystalline form of this compound. We observe significant anisotropy in the absolute values of magnetization (indicating that the easy axis is c-axis) as well as in features due to magnetic ordering in the plot of magnetic susceptibility χ versus temperature T at low temperatures. The χ(T) data reveal that there is a pseudo-low-dimensional magnetic order setting in at 4.8 K, with a three-dimensional antiferromagnetic order setting in at a lower temperature (3.8 K). A new finding in the χ(T) data is that, for H∥〈1 1 0〉 but not for H∥〈0 0 1〉, there is a broad shoulder in the range 8–20 K, indicative of the existence of magnetic correlations above 5 K as well, which could be related to the previously reported slow-relaxation-dominated Mössbauer spectra. Interestingly, the temperature coefficient of electrical resistivity is found to be isotropic; no feature due to magnetic ordering could be detected in the electrical resistivity data at low temperatures, which is attributed to magnetic Brillioun-zone boundary gap effects. The results reveal the complex nature of magnetism of this compound.     

Magnetic behavior of nanocrystalline CoFe2O4

Magnetic nanoparticles of CoFe₂O₄ have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. One of the nanoparticles demonstrated a constricted magnetic hysteresis loop with no or small coercivity and remanence at low magnetic field. However, the loop opens up at high magnetic field. This magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe₂O₄ nanoparticles were synthesized under an applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments that produce Co ions and vacancies disorder.     

Infrared reflectance of single crystal tetragonal GeO2

The transverse and longitudinal optical phonon frequencies of tetragonal GeO₂ have been determined by standard i.r. reflectance measurements employing classical dispersion theory to fit the experimental data. The static and high-frequency dielectric constants, as derived from the data, are also presented.     

Magnetic properties of CuCr2Se4 single crystals

The magnetic properties of CuCr₂Se₄ single crystals, which were grown by chemical transport reactions using iodine as a carrier, have been investigated. The magnetic moment at 0 K is found to be 5.07 μ_B per mole. The susceptibility at high temperatures follows a Curie-Weiss law with an asymptotic Curie temperature 430 K and a Curie constant 2.55 emu · $\text{deg}\text{mol}$. The magnetocrystalline anisotropy constants K₁ and K₂ are ? 6.9x 10⁵ and ? 0.9x 10⁵$\text{erg}\text{cm}{}^3$, respectively, at 5.1 K.In order to examine the effects of annealing on the magnetocrystalline anisotropy, the ferromagnetic resonance at room temperature was measured after annealing in vacuum and subsequently in an atmosphere of Se. It is found that the absolute values of K₁ and K₂ decrease after annealing in vacuum and increase to the initial values after annealing in an atmosphere of Se.     

Free induction decay in single crystal CaF2

The free induction decay in CaF₂ has been calculated with the help of the simple model. The method allows to clarify the physical nature and to compute some parameters of the nuclear magnetic resonance spectra.     

Structural determination of CoIn2S4 single crystal spinel

Single crystals of the spinel CoIn₂S₄ were grown by iodine vapor transport. The structural determination leads to Fd3m space group with Co²⁺ ions distribution between O_h (63%) and T_d (37%) sites of the spinel structure.     

Bi2ZnOB2O6单晶偏振拉曼光谱

本文通过分析不同几何配置下的偏振拉曼光谱对非线性光学晶体的晶格振动模式进行了研究. 首先根据因子群分析,将晶体的振动模按晶体对称群的不可约表示进行分类,其次测量了晶体在10–1600 cm^-1范围内,不同几何配置下的偏振拉曼光谱,并在此基础上指认了晶体的晶格振动模式. 300 cm^-1以下的振动峰,归结为晶体的外振动,来自[BiO₆],[ZnO₄],[BO₄]和[BO₃]原子基团的平动和转动;300cm^-1以上为晶体的内振动,主要与Bi-O,和Zn-O键振动有关. 晶体拉曼光谱中最高振动频率达到1407 cm^-1,被指认为[BO₃]三角形中B-O键的伸缩振动,体现了[BO₃]基团中高的电子非局域化程度. 关键词： 2ZnOB₂O₆单晶')" href="#">Bi₂ZnOB₂O₆单晶 偏振拉曼光谱 振动模式