Cu含量对Ni_(55)Fe_(18)Ga_(27)合金结构和磁性的影响

系统研究了Cu分别替代Fe和Ni对Ni_(55)Fe_(18)Ga_(27)结构和磁性的影响.结果表明:熔炼Ni_(55)Fe_(18-x)Cu_xGa_(27 )(x=1, 2, 3, 4)虽仍为奥氏体相结构,但伴有γ相出现;居里温度随Cu含量增加而降低,这是由于Cu掺杂引起过渡金属近邻原子间相互交换作用减弱所致;交流磁化率随Cu含量增加而降低,原因在于Fe是磁性的主要贡献者,Cu替代Fe会削弱Fe的磁矩,从而导致合金磁性降低.熔炼、退火和甩带Ni_(51)Cu_4Fe_(18)Ga_(27)均存在马氏体相变.熔炼样品马氏体相变温度最高,退火和甩带样品基本相同.这一特点表明热处理方式能够改变原子排列的有序度,因此可以通过改变热处理方式来调控马氏体相变温度.     

Study of low temperature ferromagnetism,surface paramagnetism and exchange bias effect in α-Fe1.4Ga0.6O3 oxide

The compound α-Fe_1.4Ga_0.6O₃ has been prepared by mechanical alloying of α-Fe₂O₃ and β-Ga₂O₃ and subsequent heating under vacuum condition. X-ray diffraction, Raman and Mössbauer spectroscopy confirmed stabilization of the material in rhombohedral phase. A remarkable change in the magnetic ordering has been found by substitution of non-magnetic Ga atoms in α-Fe₂O₃. The ferromagnetism in α-Fe_1.4Ga_0.6O₃ is found to be more soft and enhanced in comparison to α-Fe₂O₃. The samples also exhibited features of exchange bias, low temperature surface paramagnetism, and suppression of Morin transition. Nano-sized grains and alloying process of the material affected these features up to certain extent. The results of magnetic measurements are highly interesting for designing metal doped α-Fe₂O₃ based ferromagnet for room temperature applications.     

R型铁氧体BaFe4-xTi2+xO11的化学组态以及磁性行为的研究

本文通过传统的固相反应法制备了R型六角铁氧体BaFe_4-xTi_2+xO₁₁ (x= 0, 0.25, 0.5, 0.75, 1), 并且对它的原子价态以及磁性行为进行了研究. X 射线光电子能谱(XPS)结果显示了随着掺杂含量的增加, 体系中Fe³⁺离子逐渐减少而Fe²⁺离子逐渐增加. 由于具有非对称结构的阻挫晶格中存在各种关联作用的竞争, 使得BaFe_4-xTi_2+xO₁₁体系表现出了复杂的磁有序行为, 在T₁～250 K和T₂～83 K两处存在磁转变. 对这一系列掺杂样品, 在相变温度T₁之上表现顺磁行为, 而在相变温度T₂前后的磁化强度都表现出低场下随磁场的增加快速增加, 高场下则线性变化且在5×10⁴ Oe时还未达到饱和的行为, 表明这一系列掺杂样品是典型的倾斜反铁磁态(canted antiferromagnetic) 或者亚铁磁态.     

磁二向色性光电发射

磁二向色性光电发射（ Ｍ Ｄ Ｐ Ｅ） 技术是结合光电子能谱和磁二向色性技术的磁学测量方法,近年来已成为研究表面、界面和薄膜等低维体系磁性的重要手段。本文概述了其基本原理和实验方法,着重探讨几种 Ｍ Ｄ Ｐ Ｅ 效应的产生及其理论解释,并介绍了 Ｍ Ｄ Ｐ Ｅ 在磁性过渡金属、稀土金属低维体系中的应用。     

Spin–phonon coupling in van der Waals antiferromagnet VOCl

We report magnetization and Raman spectroscopy study on single crystals of VOCl, a van der Waals antiferromagnetic material. Magnetization measurement confirms an antiferromagnetic transition at 79 K and a magnetic easy axis along crystallographic a direction. The temperature-dependent Raman spectrum reveals five peaks at 30 K. Below the Neel temperature TN, the Raman-active modes 247 cm~(-1) and 404 cm~(-1) remarkably deviate from the standard Boltzmann function,which is ascribed to the strong magnetoelastic coupling between spins and phonons. We further observe an anomaly in 383 cm~(-1) mode at around 150 K. This coincides with the broad maximum in VOCl's magnetic susceptibility, suggesting a development of short-ranged magnetic order at this temperature.     

Derivation of Magnetized-Wire Metrics in 5-Dimensional General Relativity

An infinite class of magnetized line-source (wire) metrics are here derived within the 5D GR (Kaluza-Klein) formalism. These metrics are cylindrically-symmetric (thus representing line-sources), and off-diagonal (thereby representing magnetized wire sources). The off-diagonality of these metrics is significant as all prior cylindrically-symmetric 5D GR metrics have been diagonal. In Kaluza-Klein theory, the vector potentials of EM are incorporated into the extended off-diagonal components of the metric. Thus, examination of such off-diagonal line source (magnetized wire) metrics is a hitherto untapped potential for 5D GR investigation.     

Synthesis, crystal structure and magnetic properties of a novel manganese(II)-nitronyl nitroxide-azido(μ_(1,1) and μ_(1,3)) one-dimensional complex

A novel one-dimensional manganese(Ⅱ) complex containing nitronyl nitroxide radical [Mn2(IM2-py)2(Ac)2((μ1.1-N3)(μ1,3-N3) . EtOH]n was synthesized and characterized structurally and magnetically. It crystallizes in the monoclinic space group p21/n. Each Mn(Ⅱ) ion is six-coordinated in a distorted octahedral environment. The two N atoms of the nitronyl nitroxide radical and the two O atoms of acetate ligands are in the equatorial plane, whereas the two different azido bridging ligands are in trans axial position. Mn(Ⅱ) ions are linked by nitrogen atom of μ1,1-azido and oxygen atoms of two carboxy groups to form a Mn-Mn unit. Mn-Mn units are linked by azido ligands through u1,3 bridging style to form a one-dimensional chain. The compound is connected by the coordination bonds,π-π interactions and hydrogen bonds as a three-dimensional structure. Magnetic susceptibility data support that there are stronger antiferromagnetic interactions between the radical and Mn(Ⅱ) ion, weak antiferromagnetic inter     

An introduction to molecular spintronics

We review the progress and future possibilities in the emerging area of molecular spintronics. We first provide an overview of the different transport regimes in which electronic nanodevices can operate, then briefly overview the important characteristics of molecular magnetic materials that can be useful for application in spintronics and we eventually present several schemes to include such systems into spintronic nanodevices. We hightlight the importance of a chemical approach to the area, and in the last section we showcase some approaches to the creation of hybrids made of carbon nanostructures and molecular magnets, which are gaining increasing attention.     

Metal‐Ion Metathesis in Metal–Organic Frameworks: A Synthetic Route to New Metal–Organic Frameworks

A porous metal–organic framework, Mn(H₃O)[(Mn₄Cl)₃(hmtt)₈] (POST‐65), was prepared by the reaction of 5,5′,10,10′,15,15′‐hexamethyltruxene‐2,7,12‐tricarboxylic acid (H₃hmtt) with MnCl₂ under solvothermal conditions. POST‐65(Mn) was subjected to post‐synthetic modification with Fe, Co, Ni, and Cu according to an ion‐exchange method that resulted in the formation of three isomorphous frameworks, POST‐65(Co/Ni/Cu), as well as a new framework, POST‐65(Fe). The ion‐exchanged samples could not be prepared by regular solvothermal reactions. The complete exchange of the metal ions and retention of the framework structure were verified by inductively coupled plasma–atomic emission spectrometry (ICP‐AES), powder X‐ray diffraction (PXRD), and Brunauer–Emmett–Teller (BET) surface‐area analysis. Single‐crystal X‐ray diffractions studies revealed a single‐crystal‐to‐single‐crystal (SCSC)‐transformation nature of the ion‐exchange process. Hydrogen‐sorption and magnetization measurements showed metal‐specific properties of POST‐65.