硅酸三钙穆斯堡尔谱的研究

对1550℃下锻烧、空气中淬冷的不同α—^(57)Fe_2O_3含量的3CaO、SiO_2(以下简称C_3S)系列样品进行穆斯堡尔谱研究,确定它的铁离子价态、自旋态、占位情况及其与α—^(57)Fe_2O_3含量的关系,析出相和铁含量的关系。研究结果表明:在氧化气氛中进入C_3S中的铁离子约5%以高自旋Fe^(2+)形态出现,在低铁含量的样品中,尚有8%可能是低自旋二价铁Fe^(II)。这一结果与前人的研究有所不同。此外对铁的占位情况与固溶度的关系、Fe^(2+)的出现提出一些看法。

RELAXATION PROCESS IN COBALT-FERRITE EPITAXIAL IRON OXIDES

The migration process of Co ions in the cobalt-ferrite epitaxial layer on γ-Fe_(2)O_(3) powder has been studied by magnetic thermal annealing method.The activation energy E and coefficient A of Co ions have been measured.An abnormal increase of coercivity of sample annealed in a transverse magnetic field was found.On the basis of Mdssbauer and XPS results the reason of this phenomenon is discussed.

A NEW WEAK ITINERANT FERROMAGNET ζFe_(2)N

ζ Fe_(2)N has been identified as a new weak itinerant ferromagnet by magnetic measurements.It has the highest ratio q_(c)/q_(s) of effective atomic moment qc to the atomic moment q_(s),and a low Curie temperature T_(c)=7K.The magnetic properties were analysed according to the Stoner-Edwards-Wohlfarth(SEW)model,which give results,in agreement with the magnetization and susceptibility measured at temperatures below T_(c).

Al_(86-x)Fe_(14+x)准晶相合金的M6ssbauer谱

本文研究了Al_(86-x)Fe_(14+x)(x=0,2,4,6,8.5)准晶相合金的Mossbauer谱,结果表明对x=0的Al_(86)Fe_(14)合金中以decagonal准晶相为主,谱拟合结果为两套面积积分比为1.69,近于黄金分割的亚谱组成,支持了准晶相为两种“Penrose”多面体组成的观点。当x增加时,出现的晶态含量增加;x=8.5时,几乎全部为晶态Al_3Fe相。

YBa_2Cu_(3-x)Fe_xO_y的离子配位与结构转变

本文用穆斯堡尔效应、X射线衍射等手段,系统研究了掺铁的YBa_2Cu_(3-x)Fe_xO_y(0.01≤x≤0.2)超导氧化物经过不同温度真空退火后超导转变温度T_c、相结构、氧含量与氧配位之间的关系,结果表明,铁主要占Cu(1)位,铁含量的增加和高温真空退火都引起正交相向四方相转变,T_c逐渐减小至零,但这两种转变过程的铁的配位结构和氧含量却不相同,对前者,相变是与出现相当数量的六配位Fe^(3+)相联系的,因此氧含量增加,对于后者,随着退火温度增加,具有二配位的铁离子增加,氧含量减少,相变是与二配位占主导相联系的,上述两种过程造成Cu-O面的破坏,使T_c降低,此外,还讨论和确定了不同晶位铁的价态。