共查询到20条相似文献,搜索用时 15 毫秒
1.
R.R. Doshi P.S.R. Krishna D.G. Kuberkar 《Journal of magnetism and magnetic materials》2009,321(19):3285-3289
We report the results of the temperature-dependent neutron diffraction measurements on the nearly half-doped (La0.325Tb0.125)(Ca0.3Sr0.25)MnO3 manganite sample. The simultaneous doping of magnetic Tb3+ and divalent Sr2+ in the La0.7Ca0.3MnO3 system results into a large A-site size disorder. Rietveld refinement of neutron diffraction data reveal that the single phase sample crystallizes in a distorted orthorhombic structure. Increased 〈rA〉 value affects the transport behavior that results into an insulating-like behavior of the sample. Under application of 1 T field sample exhibit insulating-like behavior while insulator-metal transition (TIM) is exhibited under 5 and 8 T fields. Variable range hoping (VRH) mechanism of charge carriers is exhibited in the insulating region. Field cooled and zero field cooled magnetization measurement shows the Curie temperature (TC)~47 K. The refinement of the ND data collected at various temperatures below 300 K shows that there is no structural phase transition in the compound. Around 100 K, a magnetic peak appears at lower angle that can be ascribed to the presence of the A-type antiferromagnetic (AFM) phase. Two more peaks are observed around 50 K at lower angles that can be fitted in CE-type antiferromagnetic phase. Splitting of the peaks at lower temperatures is the signature of orbital ordering in the presently studied nearly half-doped manganite system. Results of the detailed structural analysis of the temperature-dependent ND measurements on (LaTb)0.45(CaSr)0.55MnO3 sample has been discussed in the light of coexisting A-type and CE-type antiferromagnetic phases present in the sample at low temperature. 相似文献
2.
Z. Hossain A.K. Rajarajan C. Geibel 《Journal of magnetism and magnetic materials》2009,321(3):213-215
The magnetic properties of polycrystalline PrRh2Si2 sample have been investigated by neutron diffraction measurements. Antiferromagnetic transition with an anomalously high ordering temperature (TN∼68 K) is clearly observed in magnetic susceptibility, specific heat, electrical resistivity and neutron diffraction measurements. Neutron diffraction study shows that Pr3+ ions carry an ordered moment of 2.99(7)μB/Pr3+ and align along the crystallographic±c-directions for the ions located at the (0,0,0) and positions. The magnetoresistance at 2 K and 10 T is rather large (∼35%). 相似文献
3.
G.V. Bazuev A.V. Korolyov T.I. Chupakhina 《Journal of magnetism and magnetic materials》2010,322(5):494-312
Two methods—the solid-phase high-temperature (1300 °C) and the liquid-phase low-temperature (750 °C) routes—were used to synthesize the complex oxide La1.25Sr0.75MnCoO6, which has the structure of rhombohedral perovskite and is characterized by a disordered distribution of Mn and Co in structural sites. It was found by means of X-ray absorption near edge spectroscopy (XANES) at the K-edge that mixed valence states of Co2+/Co3+ and Mn3+/Mn4+, exist in both phases. Measurements of dc magnetization and real (χ′) and imaginary (χ″) parts of the ac susceptibility showed that the magnetic properties of these oxides are determined by a ferromagnetic transition at TC=217 K and a frequency-dependent transition at Tg<100 K. The high frequency dependence of Tg is indicative of the cluster-glass behavior of La1.25Sr0.75MnCoO6 (7 5 0) at T<TC within the ferromagnetic state. 相似文献
4.
We report neutron diffraction measurements on CeNi4Mn, which has recently been identified as a soft ferromagnet with a sizeable spin-transport polarization. Our data show conclusively that the Mn atoms occupy a unique site (4c) in the unit cell, which has the symmetry of the cubic MgCu4Sn-type structure. We infer a moment of 4.6 μB on Mn at 17 K, which is oriented ferromagnetically along the {101} plane. The amplitude of the Mn vibrational motion is found to be larger than that of Ce and Ni atoms at all temperatures, thereby lending support to theoretical prediction of rattling phonon modes in this compound. 相似文献
5.
Temperature and field-dependent magnetization measurements on polycrystalline CeMnCuSi2 reveal that the Mn moments in this compound exhibit ordering with a ferromagnetic (FM) component ordered instead of the previously reported purely antiferromagnetic (AFM) ordering. The FM ordering temperature, Tc, is about 120 K and almost unchanged with external fields up to 50 kOe. Furthermore, an AFM component (such as in a canted spin structure) is observed to be present in this phase, and its orientation is modified rapidly by the external magnetic field. The Ce L3-edge X-ray absorption result shows that the Ce ions in this compound are nearly trivalent, very similar to that in the heavy fermion system CeCu2Si2. Large thermomagnetic irreversibility is observed between the zero-field-cooled (ZFC) and field-cooled (FC) M(T) curves below Tc indicating strong magnetocrystalline anisotropy in the ordered phase. At 5 K, a metamagnetic-type transition is observed to occur at a critical field of about 8 kOe, and this critical field decreases with increasing temperature. The FM ordering of the Mn moments in CeMnCuSi2 is consistent with the value of the intralayer Mn–Mn distance RaMn–Mn=2.890 Å, which is greater than the critical value 2.865 Å for FM ordering. Finally, a magnetic phase diagram is constructed for CeMnCuSi2. 相似文献
6.
H. Gamari-Seale I.O. Troyanchuk K.L. Stefanopoulos 《Physica B: Condensed Matter》2008,403(17):2924-2929
In this paper we report the study of the perovskites La0.7Ca0.3Mn0.5Co0.5O3 and La0.8Sr0.2Mn0.5Co0.5O3 by neutron powder diffraction at various temperatures and magnetization measurements in zero applied field and at low cooling regimes. The replacement of half Mn by Co in La0.7Ca0.3MnO3 and La0.8Sr0.2MnO3 destroys their long-range ferromagnetism exhibiting a cluster glass ferromagnetic order similar to the one observed in many cobaltites. 相似文献
7.
8.
The structural and magnetic properties of ErMn2H4.6 have been studied by X-ray and neutron diffraction up to the pressures of 15 and 6 GPa, respectively. In the pressure range 0<P<3 GPa we observe a first-order phase transition to new high-pressure (HP) phase. The HP phase has the same hexagonal unit cell as the ambient-pressure phase but smaller lattice parameters (ΔV/V=−5%). The structural transition results in suppression of the long-range antiferromagnetic order. Our results suggest that pressure changes positions of the hydrogen atoms in the metal host. We speculate that the new arrangement of hydrogen atoms induces spin frustration and, therefore, suppresses long-range magnetic order in the HP phase. 相似文献
9.
In a temperature dependent neutron powder diffraction (NPD) study we observed the high temperature cubic phase at 973 K in the polycrystalline double perovskite Sr2MnWO6. Rietveld analysis of the NPD data shows that the room temperature tetragonal phase exists up to 573 K (space group P42/n, a=8.0119 (4) Å, c=8.0141(8) Å). At 773 K, the primitive tetragonal symmetry change to body-centred tetragonal (space group I4/m, a=5.6935(5) Å, c=8.077(1) Å) and finally at 973 K it becomes face-centred cubic (space group Fm-3m, a=8.0864(8) Å). The changes in the structural symmetry are connected to the small distortion of the B-site octahedra, which are insensitive to the Differential Thermal Analysis (DTA) signal. 相似文献
10.
In this work neutron diffraction studies of Tb2Rh3Si5 compound are reported. The compound crystallizes in the monoclinic crystal structure of Lu2Co3Si5-type. At 1.5 K an antiferromagnetic ordering with a propagation vector k=(1/2;1/2;1/2) was observed. The Tb magnetic moments of 9.8(2) μB form a non-collinear magnetic structure. In the vicinity of Néel temperature of 8 K a change of the magnetic ordering is evidenced. The change seems to be connected with phase transition from commensurate to incommensurate sine-wave modulation of the Tb magnetic moments. 相似文献
11.
Magnetic susceptibility, heat capacity and electrical resistivity measurements have been carried out on a new ruthenate, La2RuO5 (monoclinic, space group P21/c) which reveal that this compound is a magnetic semiconductor with a high magnetic ordering temperature of 170 K. The entropy associated with the magnetic transition is 8.3 J/mol K close to that expected for the low spin (S=1) state of Ru4+ ions. The low temperatures specific heat coefficient γ is found to be nearly zero consistent with the semiconducting nature of the compound. The magnetic ordering temperature of La2RuO5 is comparable to the highest known Curie temperature of another ruthenate, namely, metallic SrRuO3, and in both these compounds the nominal charge state of Ru is 4+. 相似文献
12.
A. Szytu?a ?. Gondek A. Arulraj B. Penc 《Journal of magnetism and magnetic materials》2009,321(20):3402-3405
Physical properties of NdAu2Ge2, crystallising with the tetragonal ThCr2Si2-type crystal structure, were investigated by means of magnetic, calorimetric and electrical transport measurements as well as by neutron diffraction. The compound exhibits antiferromagnetic ordering below TN=4.5 K with a collinear magnetic structure of the AFI-type. The neodymium magnetic moments are parallel to the c-axis and amount to 1.04(4) μB at 1.5 K. The observed magnetic behaviour is strongly influenced by crystalline electric field effect. 相似文献
13.
I.O. Troyanchuk M.V. Bushinsky H. Szymczak M. Baran K. Bärner 《Journal of magnetism and magnetic materials》2007
Powder neutron diffraction and magnetic studies have been performed for NdMn0.5Fe0.5O3 and NdMn0.5Cr0.5O3 manganites. In NdMn0.5Cr0.5O3, magnetic structure has been revealed consisting of ferromagnetic and G-type antiferromagnetic components as result of a 3d-ions magnetic moments ordering. Magnetic moments of Nd-ions are parallel to the ferromagnetic component. In NdMn0.5Fe0.5O3 only the antiferromagnetic G-type structure has been found whereas Nd-sublattice was not ordered. In the both compounds, magnetic moments of 3d-ions are significantly less than one can expect, what is interpreted in terms of intrinsic chemical inhomogeneity. Magnetic phase diagrams have been constructed for the Nd(Mn1−xMx)O3 (M=Fe, Cr) systems, interpreted assuming superexchange interactions Mn3+–O–Cr3+ to be positive, Mn3+–O–Fe3+ negative and taking into account a disordered arrangement of Mn and Cr ions in the crystal structure sublattice as well as interplay between Jahn–Teller effect and superexchange interactions. 相似文献
14.
M. P?ka?a K. P?ka?a J.F. Fagnard 《Journal of magnetism and magnetic materials》2010,322(21):3460-3463
The polycrystalline manganite La0.75Sr0.25MnO3 prepared by an alternative carbonate precipitation route reveals the rhombohedral perovskite structure. Magnetization isotherms measured up to 2 T are used to determine Curie temperature of 332 K by means of Arrott plot. Maximum of magnetic entropy change is found at Curie temperature. The relative cooling power equal to 64 J/kg for 1.5 T magnetic field, is superior as compared to the manganite with the same chemical composition from the sol-gel method. 相似文献
15.
The crystal and magnetic structure of Ho2NiGe6 was studied by powder neutron diffraction. The paramagnetic neutron diffraction data confirmed the Ce2CuGe6-type crystal structure reported earlier for this compound. Below the Néel temperature equal to 11 K the Ho magnetic moments form a uniaxial antiferromagnetic ordering. The Ho magnetic moments equal to 8.16(7)μB at 1.5 K are parallel to the b-axis. The data are compared with those published for HoNi0.46(6)Ge2. 相似文献
16.
W.D. Hutchison D.J. Goossens K. Nishimura K. Mori Y. Isikawa A.J. Studer 《Journal of magnetism and magnetic materials》2006
Magnetisation and specific heat measurements, in the range 2 K to room temperature, demonstrate that three magnetic phases exist for the intermetallic compound TbNiAl4. Powder neutron diffraction, also carried out over a wide temperature range, establishes that the intermediate magnetic phase is incommensurate, and confirms that the lowest temperature phase has a linear antiferromagnetic structure with a (0 1 0) propagation vector. The respective transition (Néel) temperatures, in zero applied magnetic field are 34.0 and 28.0 K. 相似文献
17.
A.C. Mclaughlin 《Solid State Communications》2006,137(7):354-357
A magnetic, electronic and structural study of the double perovskites Ba2REMoO6 (RE=Sm, Eu, Gd, Dy) has been performed. All materials crystallise in the cubic symmetry space group and the cell volume decreases as RE varies from Sm to Dy in accordance with Vegard's law. An antiferromagnetic transition is observed below TN=130 and 112 K for RE=Sm and Eu, respectively. The Néel temperatures of these ordered rare earth molybdenum double perovskites are much higher than previously observed in double perovskites containing Eu or Sm and a 4d or 5d transition metal arranged in an ordered rock salt configuration. The high Néel temperatures arise due to a strong superexchange magnetic interaction via the Mo-O-RE-O-Mo pathway. All of the phases are electronically insulating and there is no evidence of magnetoresistance at any temperature. 相似文献
18.
We have investigated the pressure-induced structural phase transition in ReO3 by neutron diffraction on a single crystal. We collected neutron diffraction intensities from the ambient and high pressure phases at P=7 kbar and refined the crystal structures. We have determined the stability of the high pressure phase as a function temperature down to T=2 K and have constructed the (P-T) phase diagram. The critical pressure is Pc=5.2 kbar at T=300 K and decreases almost linearly with decreasing temperature to become Pc=2.5 kbar at T=50 K. The phase transition is driven by the softening of the M3 phonon mode. The high pressure phase is formed by the rigid rotation of almost undistorted ReO6 octahedra and the Re-O-Re angle deviates from 180°. We do not see any evidence for the existence of the tetragonal (P4/mbm) intermediate pressure phase reported earlier. 相似文献
19.
The mechanical spectrum of bilayer cuprate La1.82Sr0.18CaCu2O6+δ (La2126) was measured using the vibrating reed method from 30 K to room temperature at kilohertz frequency. A clear modulus softening was observed at 223 K accompanied by a sharp internal friction peak, which evidences a phase transition. Another broad internal friction peak around 250 K was observed, accompanied by a large modulus change. This contrasts with the broad internal friction peak of Ca doped Y Ba2Cu3O7−δ (Y123) for which no clear modulus change was observed. The main contribution to the broad internal friction peak of La2126 is expected to be from the glass transition of the interstitial oxygen atoms. 相似文献
20.
Using high-resolution time-of-flight neutron powder diffraction, the crystal structure of BaPbO3 has been reinvestigated at room temperature and 4.2 K. By comparing different structural models, i.e. the orthorhombic Imma and the monoclinic I2/m, it is concluded that the former one describes correctly the structure of BaPbO3, and no Imma→I2/m phase transition exists in the temperature range investigated. The apparent monoclinic distortion is likely due to the existence of twins that introduce the micro strain resulting in anisotropic line broadening of the observed profiles. 相似文献