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Effects of adding different types of carbon on the structure and magnetic properties of SmCo_(6.9)Hf_(0.1) alloy

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Journal of Rare Earths 2013年第12期31卷 1168-1174页

作者：孙继兵步绍静杨薇王洪水崔春翔何辰辉 Key Laboratory for New Type of Functional materials in Hebei Province School of Materials Science and EngineeringHebei University of Technology

In this paper,SmCo6.9 Hf0.1 as-cast alloys and ribbons with the addition of either graphite（C） or carbon nanotubes（CNTs） were prepared by arc melting and melt-spinning,*** effects of adding carbon on the structure and magnetic properties SmCo6.9 Hf0.1 were investigated by means of X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,magnetic force microscopy（MFM） and vibrating sample magnetometer（VSM）.It was found that the microstructure and magnetic structure of SmCo6.9 Hf0.1 ribbons were changed obviously due to the introduction of C or CNTs,although their crystal structure was characterized as the same Sm（Co,Hf）7 single phase,no matter carbon was added or *** a result,the magnetic properties of carbon-contained ribbons were enhanced in a certain *** was considered to be related to the refined equiaxed grains,small domain size and the pinning effect of C or CNTs-rich *** magnetic properties of SmCo6.9 Hf0.1（CNTs）0.05 ribbons reached Hc =12.5 kOe,Mr =57.0 emu/g and Mr/M2 T =0.788.

关键词： magnetically ordered materials rapid-solidification crystal structure magnetic measurements rare earths

Exchange coupling and helical spin order in the triangular lattice antiferromagnet CuCrO_2 using first principles

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Chinese Physics B 2012年第7期21卷 498-504页

作者：江学范刘先锋吴银忠韩玖荣 Jiangsu Key Laboratory of Advanced Functional materials Changshu Institute of Technology College of Physics Science and Technology Yangzhou University

The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approxi- mations （GGA）＋U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non- collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with （110） spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a＋ b directions, each with a screw-rotation angle of about I20°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.

关键词： magnetically ordered materials multiferroic spin frustration spin orbit effects

Renormalization of spin polarised itinerant electron bands in the normal state of a model ferromagnetic superconductor

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Chinese Physics B 2011年第3期20卷 382-385页

作者：马磊黄爱群李俊 National Laboratory of Solid State Microstructures and Department of Physics Nanjing University Department of Physics and Electronic Engineering Zaozhuang University

This paper studies the normal state properties of itinerant electrons in a toy model, which is constructed according to the model for coexisting ferromagnetism and superconductivity proposed by Suhl [Suhl H 2001 Phys. Rev. Lett. 87 167007]. In this theory with ferromagnetic ordering based on localized spins, the exchange interaction J between conduction electrons and localized spin is taken as the pairing glue for s-wave superconductivity. It shows that this J term will first renormalize the normal state single conduction electron structures substantially. It finds dramatically enhanced or suppressed magnetization of itinerant electrons for positive or negative J. Singlet Cooper pairing can be ruled out due to strong spin polarisation in the J 〉 0 case while a narrow window for s-wave superconductivity is opened around some ferromagnetic J.

关键词： magnetically ordered materials exchange and superexchange superconductor

Investigation of the crystal structure and magnetic properties of Nd_(3-x)GdxCo_(11)B_4 borides

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Journal of Rare Earths 2011年第5期29卷 466-470页

作者： Seluk Kervan Nazmiye Kervan Ayse zdemir Hseyin Szeri Nevsehir University Faculty of Arts and SciencesPhysics Department TUBTAK-UME National Metrology Institute

Polycrystalline samples of pseudo-ternary intermetallic Nd3–xGdxCo11B4 （x=0,1,2,3） borides prepared by standard arc-melting were characterized by X-ray powder diffraction （XRPD）,magnetization and differential scanning calorimetry （DSC） measurements. The X-ray diffraction patterns indicated the hexagonal Ce3Co11B4-type structure with P6/mmm space group for each composition. The substitution of Gd for Nd led to a decrease of the unit-cell parameters a and the unit-cell volume V,while the unit-cell parameter c increased linearly. Magnetic measurements indicated that all samples were ordered magnetically below the Curie temperature. The Curie temperatures increased as Nd was substituted by Gd. The saturation magnetization at 4 K decreased upon the Gd substitution up to x=1,and then increased.

关键词： intermetallics magnetically ordered materials magnetic measurements rare earths

Induced modifications in the properties of Sr doped BiFeO3 multiferroics

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Progress in Natural Science:materials International 2013年第5期23卷 487-492页

作者： Tanvir Hussain Saadat A.Siddiqi Shahid Atiq M.S.Awan Centre of Excellence in Solid State Physics Quaid-e-Azam CampusUniversity of the Punjab Interdisciplinary Research Centre in Biomedical materials (IRCBM) COMSATS Institute of Information Technology Department of Physics COMSATS Institute of Information Technology

Multiferroics exhibit unique combination of ferroic properties,*** instance,in BiFeO3,magnetic and electric properties *** this work,BiFeO3 and Sr-doped BiFeO3 samples with general formula,Bi1-x Srx FeO3(x=0.00,0.05,0.10,0.20,and 0.30) were synthesized by sol-gel auto-combustion technique,in order to investigate these ferroic *** samples were confrmed to have perovskite type rhombohedral structure,characteristic of BiFeO3.A dilute phase of Bi2Fe4O9was also found in all the Sr-doped *** micrographs of the palletized samples revealed that minutely doped Sr might not have any effect on the morphology of the *** dependent dielectric measurements were carried out at room temperature for all the samples from 100 Hz to 1 *** dielectric constant of un-doped sample at low frequency was 52 which decreased with increasing Sr *** enhancement of magnetic properties was observed with increasing the Sr *** BiFeO3 material was observed to have the least value of remanent *** the Sr2+ tions were doped in BiFeO3,its magnetization and remanence were increased to 0.867 emu/g and 0.175 emu/g,respectively,at x=0.30.

关键词： Bismuth ferrite Ferroelectricity Ferromagnetism Nanomaterials magnetically ordered materials

Magnetoresistance Study of YCo6Ge6-type Dy0.4Sm0.6Mn6Ge6 Compound

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Journal of Rare Earths 2006年第S2期 197-199页

作者：汪汝武张立刚李亚伟陈静李云宝张国宏 Department of Applied Physics Wuhan University of Science and Technology 2. Hubei Province Key Laboratory of Refractories and Ceramics Ministry-Province Jointly-Constructed Cultivation Base for State Key Laboratory

The magnetoresistance (MR) measurements on a naturally occurring multilayer Dy0.4Sm0.6Mn6Ge6 were presented, which is ferrimagnetic below 445 K. In the temperature range below 65 K, MR displays a maximal value around 3 T and above this critical field MR decreases, in the positive direction, with fields up to 5 T. Its upturn may result from the influence of the magnetic field on the Fermi surface. It is also possible that the scattering of the conduction electrons by the nonmagnetic layers Ge becomes dominant at low temperatures.

关键词： rare-earth manganese compound magnetically ordered materials magnetoresistance