地面坐标系

讨论了地面坐标系作为近似惯性坐标系的条件;还讨论了自由落体运动的能量关系式.     

物理教学中的课堂讨论策略

课堂讨论能够在教学中最大限度地激发学生的智慧，有助于学生更好地掌握所学知识；有利于教师获得教学效果的反馈信息，及时调控教学．物理课堂讨论是教师与学生共同构建的一种教学行为，是彰显学生个性、扩大信息交流和思维容量的有效途径，因而倍受物理教师的青睐但课堂讨论又费时费力和讨论结果多变等，所以授课教师需要注意采用以下策略：     

惯性力

讨论了惯性力对惯性坐标系与惯性参照物是否有影响的问题;此外,还讨论了惯性力的测量问题.     

有关昂氏气态方程的几点讨论

本文叙述了有关昂氏气态方程(昂内斯气态方程的简称)的几点讨论.一是昂氏气态方程收缩为范式气态方程的讨论;二是昂氏气态方程温度T昂和理想气态方程温度T理相等的压强(下面简称等温压强)的讨论;三是昂氏气态方程压强P昂和理想气态方程压强P理相等的温度(下面简称等压温度)的讨论.     

有关昂氏气态方程的几点讨论

本文叙述了有关昂氏气态方程（昂内斯气态方程的简称）的几点讨论。一是昂氏气态方程收缩为范式气态方程的讨论;二是昂氏气态方程温度昂T 和理想气态方程温度T理相等的压强（下面简称等温压强）的讨论;三是昂氏气态方程压强昂P 和理想气态方程压强P理相等的温度（下面简称等压温度）的讨论。     

有关昂氏气态方程的几点讨论

本文叙述了有关昂氏气态方程(昂内斯气态方程的简称)的几点讨论.一是昂氏气态方程收缩为范式气态方程的讨论；二是昂氏气态方程温度T昂和理想气态方程温度T理相等的压强(下面简称等温压强)的讨论；三是昂氏气态方程压强P昂和理想气态方程压强P理相等的温度(下面简称等压温度)的讨论.     

“等离子体物理基础”课程讨论教学实践研究

讨论教学作为教学手段的重要表现形式，其对课程知识的扩展和教学效果的提升都具有积极作用.然而由于讨论教学具有较大的开放性，需要对讨论教学实施方法进行设计和可行性评估.“等离子体物理基础”作为选修课程，部分学生对该课程内容掌握浅显，甚至硬背结论的现象也有发生.为了改善上述情况，需开展课堂讨论教学.该教学实践表明有效的课堂讨论教学能较好地补充课程内容，增加整体教学效果，加强学生们对该课程的认识，同时也锻炼了他们的独立思考和动手能力.     

六点防雷方案中之浪涌保护的探讨

本文主要针对六点防雷方案中的电源浪涌保护进行讨论，讨论包括器件参数和产品技术两个方面．     

基础物理实验课后的思考

物理实验课的课后讨论需要引起重视,同时这是尊重和提高学生的自主创新能力的必要途径。提出物理实验课课后开设讨论答疑课的必要性和重要性。阐述了开设实验课后讨论答疑课可以采取的方式和方法,目的是实现学生与教师的综合素质在学与教的过程中相互促进与相互提高。     

相位算子在单模压缩态中的行为

本文仔细讨论了相位算子在单模压缩态光场中的行为,计算了压缩态下相位算子的平均值和涨落。在得到了严格的、普遍性的结果后我们详细地讨论了压缩真空态这一特殊情形下的结果。此外,本文还讨论了严格的结果在经典极限下的渐近行为。     

磁性材料进展

磁性材料大体上分为两类 :其一为铁磁有序的金属磁性材料 ;其二绝大多数为亚铁磁有序、具有半导体导电性质的非金属磁性材料 .5 0年代以前 ,金属磁性材料占绝对优势 ;5 0年代以后 ,非金属磁性材料发展成为磁性材料的主流 ,除电力工业用的高饱和磁化强度FeSi合金外 ,铁氧体几乎应用于各个领域 .历史似乎按螺旋形的方式发展 ,90年代后 ,金属磁性材料又以新的面貌出现 ,3d (4f,4d ,5d ,5f… )合金与化合物、非晶、纳米微晶磁性材料重领风骚 ,其性能远超越铁氧体 .纳米磁性材料将成为新的功能材料 .文章重点介绍了永磁材料与软磁材料 ,其他如磁记录材料、磁致冷材料、磁致伸缩材料等将作简单介绍 .     

Interplay between symmetry breaking and quasiperiodicity in spin chains

Summary An isotropicXY spin chain is studied in the presence of symmetry-breaking perturbations and a periodic modulation with wave vector incommensurate with the periodicity of the chain. The ground states of the system are obtained in terms of a two-dimensional area-preserving map defined on a cylinder of finite extent. The spin distributions are found to exhibit KAM and Cantorus phases with the onset of transition being the critical phase. The relationship between these three phases and the magnetic properties of the model is also studied. The presence of two competing easy axes for spin alignment results in incommensurate reentrant phase diagram with fractal boundary.     

Effects of Mg substitution on the structural and magnetic properties of Co_(0.5)Ni_(0.5-x)Mg_xFe_2O_4 nanoparticle ferrites

In this study, nanocrystalline Co–Ni–Mg ferrite powders with composition Co_(0.5)Ni_(0.5-x)Mg_xFe_2O_4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co–Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction(XRD) analysis, Fourier transform infrared spectroscopy(FTIR), field emission scanning electron microscopy(FESEM), and vibrating sample magnetometry(VSM). The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of ~ 32 nm to ~ 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from ~ 57.35 emu/g to~ 61.49 emu/g and ~ 603.26 Oe to~ 684.11 Oe(1 Oe = 79.5775 A·m-1), respectively. The higher values of magnetization Ms and Mr suggest that the optimum composition is Co_(0.5)N_(i0.4)Mg_(0.1)Fe_2O_4 that can be applied to high-density recording media and microwave devices.     

Preparation of ferromagnetic semiconducting HgCr2Se4 thin films by molecular-beam deposition

Summary Polycrystalline thin films of the ferromagnetic semiconductor HgCr₂Se₄ have been prepared for the first time on insulating MgAl₂O₄ single-crystal substrates by molecular-beam deposition and subsequent annealing with HgSe. The optimum conditions for preparing single-phase thin films of HgCr₂Se₄ were obtained. The magnetoresistance and Hall effects of these films were measured from 77 to 295 K in magnetic fields up to 1.19·10⁶ A/m. It becomes evident that these electrical properties of the films are affected by the interdiffusion layers in the films near the substrates or the magnetically disordered layers such as amorphous or grain boundaries in the films. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

Stress sensitivity coefficient in polycrystalline and amorphous ferromagnetic materials below room temperature

Summary The piezomagnetic coupling coefficient (the ?stress sensitivity?) is quantitatively investigated below room temperature and a comparison is made among polycrystalline samples and amorphous ones. The technique used is an original one. It experimentally consists in the measurement of the amplitude of magnetoelastic waves, their resonance frequency and differential susceptibility; theoretically, it consists in coupling Newton’s law of force with the piezomagnetic state equations. The results clearly show different responses of polycrystalline samples with respect to the amorphous ones; in particular the nonmonotonic behaviour of the ?stress sensitivity? for metallic glasses is interesting for establishing their actual magnetic states at low temperature.     

Ag对CoPt/Ag纳米复合膜的结构与磁性的影响

采用直流磁控溅射的方法制备了一系列(CoPt/Ag)_n多层膜，然后在不同温度下 进行了退火处理，并对其结构和磁性做了初步的表征，研究了Ag的含量以及薄膜中每一单元 厚度与总厚度对退火后薄膜的结构以及磁性能的影响.结果表明，膜厚较薄时(大约20 nm)有 利于薄膜沿(001)取向生长，Ag的加入不但能够抑制CoPt晶粒的过分长大还可以诱导薄膜的( 001)取向，使退火后的薄膜在垂直于膜面方向上的矫顽力大大增强.对于特定组分为Co ₄₀Pt₄₃Ag₁₇的薄膜，经600℃退火后已经显示了明显的(001) 取向，垂直于膜面方向上的矫顽力为5.6×10⁵ A/m，饱和磁化强度为0.65T, 并 且磁滞回线具有很好的矩形度，剩磁比(s)为0.95. 关键词： 磁记录材料 磁性薄膜 CoPt/Ag纳米复合膜     

Electronic structure and magnetic and optical properties of double perovskite Bi2 FeCrO6 from first-principles investigation

Double perovskite Bi2 FeCrO6 , related with multiferroic BiFeO3 , is very interesting because of its strong ferroelectricity and high magnetic Curie temperature beyond room temperature. We investigate its electronic structure and magnetic and optical properties by using a full-potential density-functional method. Our optimization shows that it is a robust ferrimagnetic semiconductor. This nonmetallic phase is formed due to crystal field splitting and spin exchange splitting, in contrast to previous studies. Spin exchange constants and optical properties are calculated. Our Monte Carlo magnetic Curie temperature is 450 K, much higher than any previously calculated value and consistent with experimental results. Our study and analysis reveal that the main magnetic mechanism is an antiferromagnetic superexchange between Fe and Cr over the intermediate O atom. These results are useful in understanding such perovskite materials and exploring their potential applications.     

雷达波段内磁性吸波颗粒光散射特性分析

针对目前在微波雷达隐身技术中广泛运用的吸波材料颗粒,根据米氏(Mie)散射理论对磁性吸波颗粒在雷达波段内的光散射特性进行了数值模拟和计算分析.在Mie系数中引入磁导率变量,分别计算了磁导率、折射率及颗粒粒径等参数对吸波颗粒光散射特性的影响;同时对比分析了磁性与非磁性吸波颗粒的散射光强、散射系数、吸收系数等散射特性规律.数值计算结果表明,颗粒磁特性的变化对其散射性能造成影响,磁导率的增大将使颗粒的吸收性能增强而后向散射强度减弱,有利于吸波颗粒雷达散射截面的减小,同时磁导率变化对颗粒散射特性的影响受到复折射率的制约.     

Magnetoelastic behaviour of amorphous ferromagnetic ribbons in response to an applied tensile stress

Summary The magnetization changes, ΔM, induced by an external tensile stress, σ, in metallic-glass ribbons are theoretically calculated starting from the simplified model generally used for describing the magnetoelastic coupling in amorphous metals. Taking into account the discrepancies between the ideal behaviour and the real one as revealed in commercial amorphous ribbons, we show that the experimental results, concerning ΔM as a function of σ, can be well predicted by the theoretical evaluations. On the other hand, it results that a suitable ferromagnetic ribbon can be a magnetoelastic sensor able to measure variations of ≃1 MPa up to the 100 MPa stress.

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Riassunto Le variazioni di magnetizzazione prodotte da una tensione esterna in nastri di metallo amorfo sono state teoricamente calcolate partendo dal modello semplificato generalmente adottato per descrivere l'accoppiamento magnetoelastico in detti materiali. Tenendo conto delle differenze tra il comportamento reale e quello ideale, si mostra come i risultati sperimentali, ottenuti nei nastri amorfi in commercio, possono essere ben previsti mediante le valutazioni teoriche. D'altra parte, si mostra come un nastro amorfo, opportunamente selezionato, possa rilevare variazioni di tensione di 1 MPa sino a valori base della sollecitazione di circa 100 MPa.

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Резюме Теоретически вычисляются изменения намагниченности, ΔM, индуцированные внешним растятивающим напряжением, σ, в металлических аморфных полосах, исходя из упрощенной модели, обычно используемой для описания магнитоупругой связи в аморфных металлах. Учитывая различия между идеальным поведением и реальным поведением, мы показываем, что экснериментальные результаты в коммерческих аморфных полосах для зависимости ΔM от σ могут быть получены из теоретических вычислений. С другой стороны, отмечается, что соответствующая ферромгнитная полоса может представлять магнитноупругий датчик, способный измерять изменения напряжения от ≃1 МПа вплоть до 100 МПа.

     

利用RL交流电桥测量磁性材料的居里温度

利用RL交流电桥测量了磁性材料的居里温度,并讨论了工作频率和工作电压的变化对测量结果的影响.