共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of magnetism and magnetic materials》2001,223(3):253-260
The field dependences of the magnetic moment of several GdXY1−XMn6Ge6 compounds have been analysed by a mean-field theory of several spin structures. The assumption of spiral spin structures at low temperatures in these compounds has been confirmed. In addition to this, the magnetic phase diagrams of TbMn6Ge6 and DyMn6Ge6 have been deduced from magnetisation measurements of powder samples. In contrast to GdMn6Ge6, the crystal fields of these compounds produce a variety of additional spin phases. 相似文献
2.
《Physics letters. A》1986,117(6):313-316
By making use of the calculated results of the electronic structure of d-electrons for YMn2 in the tight-binding approximation, the sublattice moments of Mn atoms in the cubic Laves phase intermetallic compound GdMn2 are shown to be canted in the opposite direction to that of the localised moments on Gd atoms and a possible spin arrangement in GdMn2 is predicted. 相似文献
3.
Yu. F. Popov A. M. Kadomtseva G. P. Vorob’ev S. S. Krotov K. I. Kamilov M. M. Lukina 《Physics of the Solid State》2003,45(11):2155-2159
Complex studies of the magnetic, magnetoelectric, and magnetoelastic properties of GdMn2O5 single crystals in strong pulsed magnetic fields are carried out in order to obtain additional indirect information on the character of the rare-earth and manganese spin ordering. It is shown that magnetic ordering of Gd3+ spins affects the manganese sublattice spin orientation and initiates new magnetic phase transitions. The observed magnetoelectric properties of the GdMn2O5 system are interpreted in terms of the theory of phase transitions. 相似文献
4.
在10—800K的温度范围内用X射线衍射方法测量了DyMn2Ge2化合物的晶格常数与温度的变化关系,观察到高温时DyMn2Ge2由顺磁状态到反铁磁状态的自发磁相变伴随着晶格常数a的负的磁弹性异常现象.在4.2K—200K的温度范围内测量了DyMn2Ge2的交流磁化率.在交换相互作用的分子场模型近似下,从理论上分析讨论了DyMn2Ge2的低温自发磁相变和场诱导的磁相变.计算了DyMn2Ge2单晶的磁化强度与温度的变化关系以及不同温度下外磁场沿晶轴c方向时的磁化曲线.理论分析和计算结果表明,温度低于33K时在DyMn2Ge2中观察到的场诱导的一级磁相变为由亚铁磁状态(Fi)到中间态(IS)相变.
关键词:
稀土-过渡族金属间化合物
磁结构
磁相变 相似文献
5.
Guo Guanghua M. V. Eremin A. Kirste N. P. Kolmakova A. S. Lagutin R. Z. Levitin M. von Ortenberg A. A. Sidorenko 《Journal of Experimental and Theoretical Physics》2001,93(4):796-804
The experimental studies of magnetic phase transitions in the layered tetragonal intermetallic compound DyMn2Ge2 are continued. The existence of spontaneous phase transitions is confirmed by the results of measurements of the temperature dependences of lattice parameters and the initial magnetic susceptibility. The measurements in strong (up to 50 T) and ultrastrong (up to 150 T) fields revealed two new field-induced magnetic transitions. The inclusion of the exchange interaction between next-to-nearest layers of manganese and the crystal field effects for the rare-earth subsystem along with the antiferromagnetic exchange interaction of nearest Mn layers has made it possible to describe the magnetic properties of DyMn2Ge2 in a wide range of magnetic fields. The parameters of these interactions are determined from a comparison of the experimental and theoretical magnetization curves and H-T phase diagrams. 相似文献
6.
V.V. Bannikov I.R. SheinV.L. Kozhevnikov A.L. Ivanovskii 《Journal of magnetism and magnetic materials》2008
Using the full-potential linearized augmented plane-wave (FP-LAPW) method with the generalized gradient approximation (GGA) for the exchange-correlation potential, we studied spin polarization induced by replacement of oxygen atoms by non-magnetic 2p impurities (B, C and N) in non-magnetic cubic SrMO3 perovskites, where M=Ti, Zr and Sn. The results show that the magnetization may appear because of the spin–split impurity bands inside the energy gap of the insulating SrMO3 matrix. Large magnetic moments are found for the impurity centers. Smaller magnetic moments are induced on the oxygen atoms around impurities. It is shown that SrTiO3:C and SrSnO3:C should be magnetic semiconductors while other compounds in this series (SrTiO3:B, SrTiO3:N and SrZrO3:C) are expected to exhibit magnetic half-metallic or pseudo-half-metallic properties. 相似文献
7.
《Journal of magnetism and magnetic materials》1995,146(3):L241-L246
55Mn nuclear magnetic resonance has been measured for both cubic C15 and hexagonal C14 HoMn2. In the ordered state, we found a high-frequency signal, which can be assigned to magnetic Mn atoms, for both C15 and C14 phases together with a low-frequency signal from non-magnetic Mn atoms. The results of the spin-spin relaxation time T2 in the ordered state and the NMR spectra in the paramagnetic state are also given to discuss the magnetic instability and the magnetic structure. 相似文献
8.
We have studied the electronic and magnetic properties of TbFexMn2−xO5 (x=0, 0.125, 0.25) samples using first-principles density functional theory within the generalized gradient approximation (GGA) schemes. The crystal structure of TbMn2O5 is orthorhombic containing Mn4+O6 octahedra and Mn3+O5 pyramids. The structure changes to monoclinic symmetry for the Fe-doping at the Mn sites. Our spin-polarized calculations give an insulating ground state for TbMn2O5 and a metallic ground state for Fe-doped TbMn2O5. Based on the magnetic properties calculations, it is found that the magnetic moment enhances with increase in the Fe-content in TbMn2O5. Most interestingly, the enhanced magnetic moment is due to a substantial reduction of the magnetic moments at the Fe sites. 相似文献
9.
《Journal of magnetism and magnetic materials》2002,238(2-3):129-139
Powder samples of GdMn2Hx hydrides, with 0⩽x⩽4.3, have been characterized by X-ray analysis and SQUID magnetometry for temperatures ranging between 4 and 375 K. The observed phase transformations as a function of temperature and hydrogen concentration are discussed and explained. The correlated changes of magnetization and susceptibility have been analyzed and the temperature dependent development of magnetic ordering of Mn and Gd atoms as a function of temperature and hydrogen content has been discussed. The structural and magnetic phase diagrams have been proposed. 相似文献
10.
The results of extensive magnetisation, X-ray and neutron powder diffraction measurements on the intermetallic compound series Ni2-xMnSb, for 0?x?1, are reported. For x ?0.4, a high degree in the C1b structure is observed, but for x?0.3, some disorder is evident. The series is ferromagnetic, with Curie temperatures rising from 368 to 732 K with decreasing nickel concentration. The magnetic moments all lie in the range (4.0±0.3)μB, with a maximum at a composition near x=0.45. The magnetic moments are largely associated with the ordered manganese sites, but it is possible that a small negative moment ?0.25μB may be associated with the “nickel sites” for x?0.3. This latter moment may be accounted for by disordered Mn atoms antiferromagnetically aligned. 相似文献
11.
The crystal and magnetic stucture of TbMn2Ge2 are determined by neutron diffraction using a powder sample. The crystal structure of this compound is of the ThCr2Si2 type with small mixing of Mn and Ge atoms between 4(d) and 4(e) positions. At RT the antiferromagnetic collinear structure consist of a+?+? sequence of ferromagnetic layers of Mn atoms with the magnetic moment parallel to the c-axis. At 85 K, the ferromagnetic ordering within the Tb sublattice is observed. The magnetic moment (~7.7 μB) is parallel to the c-axis. At 4.2 K additional reflections are observed, which correspond to antiferromagnetic components in a monoclinic unit cell. 相似文献
12.
《Physica B: Condensed Matter》2005,355(1-4):202-206
Specific heat (SH) measurements on TbMn2(H,D)2 powders have been performed in the temperature range from 2 to 350 K, in zero magnetic field and in 9 T. Due to the low heat conductivity of the samples, the measurements were carried out on a mixed Cu- and sample-powder pellet. For TbMn2, the anti-ferromagnetic phase transition was manifest by a single SH peak at TN=47 K, whereas a double SH peak at 281 and 288 K and an upturn below 5 K were observed for the hydride sample. Upon applying the magnetic field of 9 T, the SH upturn was suppressed, whereas no visible influence was found on the specific heat in the whole temperature range above 10 K as well as on the double peak. 相似文献
13.
Moumita Dey Santanu K. Maiti S. N. Karmakar 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):105-114
We examine spin dependent transport in a quantum interferometer composed of
magnetic atomic sites based on transfer matrix formalism. The interferometer,
threaded by a magnetic flux ϕ, is symmetrically attached to two
semi-infinite one-dimensional (1D) non-magnetic electrodes, namely, source
and drain. A simple tight-binding model is used to describe the bridge system,
and, here we address numerically the conductance-energy and current-voltage
characteristics as functions of the interferometer-to-electrode coupling
strength, magnetic flux and the orientation of local the magnetic moments
associated with each atomic site. Quite interestingly it is observed that,
for ϕ = ϕ
0/2 (ϕ
0 = ch/e, the elementary flux-quantum) a
logical XOR gate like response is observed, depending
on the orientation of the local magnetic moments associated with the
magnetic atoms in the upper and lower arms of the interferometer, and it
can be changed by an externally applied gate magnetic field. This aspect
may be utilized in designing a spin based electronic logic gate. 相似文献
14.
T. A. W. Beale S. B. Wilkins R. D. Johnson D. Prabhakaran A. T. Boothroyd P. Steadman S. S. Dhesi P. D. Hatton 《The European physical journal. Special topics》2012,208(1):99-106
The magneto-electric multiferroic TbMn2O5 has a complex magnetic structure in three different magnetically ordered phases. We have determined the nature of the induced
magnetic order on the oxygen sites in the commensurate magnetic phase through full linear X-ray polarisation analysis at the
oxygen K edge. This has been achieved rotating the linear polarisation of the incident beam at the source, and using multilayers to
analyse the polarisation state of the scattered X-ray beam. We have confirmed that the anisotropy of the magnetic scattering
at the oxygen edge is consistent with the anisotropy of the manganese magnetic structure. 相似文献
15.
Effects of Ga substitution for Sn on the structure and magnetic properties of TbMn6Sn6-xGax (x=0.0-1.2) compounds have been investigated by means of x-ray diffraction, magnetization measurement and 119Sn M?ssbauer spectroscopy. The substitution of Ga for Sn results in a decrease in lattice constants and unit-cell volumes. The magnetic ordering temperature decreases monotonically with increasing Ga content from 423 K for x=0.0 to 390 K for x=1.2. At room temperature, the easy magnetization direction changes from the c-axis to the ab-plane. This variation implies that the substitution of Ga for Sn leads to a decrease in the c-axis anisotropy of the Tb sublattice. An increase in the non-magnetic Ga concentration results in a monotonic decrease of the spontaneous magnetization Ms at room temperature. Since there are three non-equivalent Sn sites, 2c (0.33, 0.67,0), 2d (0.33, 0.67,0.5) and 2e (0,0,0.34) in the TbMn6Sn6-xGax compounds, the 119Sn M?ssbauer spectra of the TbMn6Sn6 and TbMn6Sn5.4Ga0.6 compounds can be fitted by three sextets. The hyperfine fields (HFs) decrease in the order of HF(2d)>HF(2e)>HF(2c), which is in agreement with the magnetic structure. 相似文献
16.
U. Gasser P. Allenspach F. Fauth W. Henggeler J. Mesot A. Furrer S. Rosenkranz P. Vorderwisch M. Buchgeister 《Zeitschrift für Physik B Condensed Matter》1997,101(3):345-352
Inelastic neutron scattering experiments of the crystal-field (CEF) splitting of the R3+ ions (R = Ho, Er, Tm) in the superconductor RNi 2 11 B2C have been performed in the paramagnetic as well as in the magnetically ordered state in order to deduce the CEF parameters which in turn determine the thermodynamic magnetic properties of these systems. The calculated ordered magnetic moments are in agreement with magnetic neutron diffraction results, i.e. both the easy axis and the size of the zero-field moments are correctly reproduced. In addition, the entropy involved in the magnetic ordering obtained from specific heat measurements is in correspondence with the number of low-lying CEF states observed in this study. Our CEF parameter set also reproduces both the behavior and the anisotropy in M/H measured for single crystals. 相似文献
17.
《Journal of magnetism and magnetic materials》1986,53(4):318-322
Tetragonal GdMn2Ge2 is a ferrimagnet at low temperatures and changes to an antiferromagnet undergoing a first-order transition at 95 K. The temperature dependence of the magnetization has been analyzed in terms of the molecular-field approximation with interactions between Gd-Gd, Gd-Mn and Mn-Mn atoms. The Gd-Mn interaction is antiferromagnetic, and this permits the appearance of the ferrimagnetic structure at low temperatures. The uniaxial anisotropy (the easy axis of magnetization is the c-axis for both Gd and Mn moments) plays an important role in the first-order ferrimagnetic to antiferromagnetic transition. 相似文献
18.
In this paper, we present our recent experimental results of magnetic and transport properties of Gd1−xLaxMn2Ge2 intermetallic compounds with the ThCr2Si2-type layered structure. The results obtained indicate that, in GdMn2Ge2, a first-order transition from a collinear antiferromagnetic to a collinear ferrimagnetic state appears with decreasing temperature at Tt3, below the Néel temperature TN. In Gd1−xLaxMn2Ge2 compounds with x=0.05 and 0.075, after ordering ferrimagnetically at Tt1, two kinds of first-order transitions from a canted ferrimagnetic to a non-collinear antiferromagnetic state and from a non-collinear antiferromagnetic to a reentrant canted ferrimagnetic state occur at Tt2 and Tt3. In Gd0.925La0.075Mn2Ge2, a field-induced metamagnetic transition from non-collinear antiferromagnetism to canted ferrimagnetism occurs at relatively low fields, accompanied by fractal like multi-step transitions, the so called “devil's stair-case”. Furthermore, a negative giant magnetoresistance (GMR) effect (Δρ/ρ15%) was observed at the field-induced metamagnetic transition. The mechanism of this negative GMR was clarified by comprehensive measurements of the resistivity on single crystals Gd0.925La0.075Mn2Ge2 and TbMn2Ge2. With further increasing x, only canted ferrimagnetism appears with a compensation temperature for 0.10<x<0.40, whereas no compensation behavior appears for x>0.50. The phase diagram obtained indicates that the overall magnetism is controlled by the Mn–Mn intralayer distance in the tetragonal c-plane, reflecting the two-dimensional arrangement of Mn atoms. 相似文献
19.
A. G. Kochur T. M. Ivanova A. V. Shchukarev A. A. Sidorov M. A. Kiskin V. M. Novotortsev I. L. Eremenko 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):625-630
The Mn3s X-ray photoelectron spectra of manganese at oms in mono-, bi-, tri-, and hexanuclear trimethylacetate Mn complexes and MnIICl2, MnIIIOOH, MnIVO2. ionic compounds were measured. The 3s spectra of the manganese atoms in MnII, MnIII, and MnIV valent states were calculated within the isolatedion approximation. The relationship between the characteristics of the Mn3s spectra and the magnetic moments of the manganese ions in the complexes is discussed. 相似文献
20.
S.?G.?Barsov S.?I.?Vorob’ev E.?I.?Golovenchits A.?A.?Dzyuba E.?N.?Komarov V.?P.?Koptev S.?A.?Kotov V.?A.?Sanina G.?V.?Shcherbakov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):705-707
The present paper is devoted to studying the multiferroics HoMnO3, YMnO3, EuMn2O5, and GdMn2O5 by means of the µSR-method. Determination of the dynamic relaxation parameter 7n and the distribution of the local magnetic fields results in a clear phase diagram. 相似文献