Sherrington-Kirkpatric自旋玻璃模型的非平衡态性质

通过动力学蒙特卡罗模拟对Sherrington-Kirkpatric （SK）自旋玻璃模型进行研究. 结果表明,弱场下自旋玻璃的磁化率在转变点非常陡峭,而比热容则呈现比较宽的转变. 同时,也成功地模拟了自旋玻璃体的年龄效应和记忆效应. 通过模拟发现,不同的弛豫时间对系统的能量影响很大,这直接导致了年龄效应和记忆效应;各向同性的SK模型不能给出实验中的交换偏移现象. 关键词： 自旋玻璃 记忆效应 年龄效应 磁化率     

量子海森堡自旋玻璃的相图：各向异性和铁磁相互作用效应

应用静态的Ｒｅｐｌｉｃａ对称自旋玻璃理论，研究了具有Ｄｚｙａｌｏｓｈｉｎｓｋｉｉ－Ｍｏｒｉｙａ（ＤＭ）各向异性和铁磁相互作用的量子海森堡自旋玻璃模型，数值计算了自１／２自旋玻璃序参数及自旋自相互作用，并在温度－铁磁耦合强度平面内得到了相应的相图，最后对结果进行了讨论。     

机器学习方法研究玻璃体系中的Gardner相变

1985 年,英国物理学家 Eliza-beth Gardner从理论上预测了在自旋玻璃模型中存在一种由全副本对称性破缺导致的复杂相变——Gardner相变.近年来的平均场理论计算表明,Gardner 相变不仅存在于自旋玻璃,也应该存在于结构玻璃中.然而,如何在实验或计算机模拟中测量 Gardner 相变对应的临界指标...     

无穷长力程反铁磁性自旋玻璃的相图

提出了反铁磁性自旋玻璃Ising模型,并据此给出其相图。 关键词：     

自旋玻璃LaFe_yNi_(5-y)的磁性研究

本文报道了金属间化合物LaFe_yNi_(5-y)(0.5≤y≤1.1)的自旋玻璃特性。测定了样品的自旋玻璃冻结温度T_f。y≤0.9时,在一定温度下,样品中发生顺磁-自旋玻璃转变,T_f近似为y的线性函数,y≥1.0时,材料将发生顺磁-铁磁-自旋玻璃转变。     

无序复杂系统中的序--2021年诺贝尔物理学奖解读

本文首先简要介绍了什么是玻璃和自旋玻璃,然后回顾了自旋玻璃理论的发展,特别是帕里西对自旋玻璃理论的贡献及该理论在其它领域的应用.最后简要介绍了帕里西在界面随机生长和随机共振方面的重要贡献.     

三维量子自旋玻璃理论(Ⅲ)──replica对称破缺解

利用推广的Ｐａｒｉｓｉ量子ｒｅｐｌｉｃａ对称破缺方案，将我们以前提出的理论推广到ｒｅｐｌｉｃａ对称破缺，获得一组新的自旋自作用和自旋玻璃序参数的自洽方程，导出局域磁化率．通过计算ｒｅｐｌｉｃａ对称破缺自由能，发现矢量自旋玻璃模型的ｍｐｌｉｃａ对称解存在着低温破缺． 关键词：     

1999年国家杰出青年科学基金获得者(物理学部分)简介(Ⅱ)

马余强(教授、博士生导师,南京大学物理系)简历1964年11月生,1993年6月在南京大学获博士学位.1993年6月被聘为南京大学物理系副教授,1995年2月被聘为正教授.1995年5月至1996年12月在巴西C′atarina大学访问,1997年10月被南京大学聘为博士生导师.主要从事凝聚态理论的研究.已取得学术成就的创新点及评价在量子自旋玻璃的热力学特性的研究中,详细地处理了量子自旋玻璃模型的临界现象和有序相不稳定性;获得了混价铁电类材料中铁电玻璃与铁电相相变,从理论上得到铁电相可与玻璃相共存,与质子玻璃相变的实验结果一致;建立了量子Hopfield自旋玻璃…     

自旋玻璃LaFeyNi5-y的磁性研究

本文报道了金属间化合物LaFe_yNi_5-y(0.5≤y≤1.1)的自旋玻璃特性。测定了样品的自旋玻璃冻结温度T_f。y≤0.9时,在一定温度下,样品中发生顺磁-自旋玻璃转变,T_f近似为y的线性函数,y≥1.0时,材料将发生顺磁-铁磁-自旋玻璃转变。 关键词：     

自旋玻璃和复杂系统

简要地介纲了自旋玻璃的特点以及基于平均场水平的理论处理：摹本理论、ＴＡＰ理论和摹本对称破缺理论．这些理论揭示了自旋玻璃具有非常丰宫的复杂结构，可以为许多其他领域的复杂系统提供一个理论模型，可以用于组合优化、神经网络、生命进化模型等研究工作中．     

A method for detection of spectral spin diffusion from minor peaks, and its application to F MAS NMR of antimony(III)-doped fluorapatite

A new technique for detecting spectral spin diffusion in solids under MAS NMR conditions that is particularly well suited for accurately measuring cross-relaxation from minor spectral components is presented. The pulse sequence, SINK (Saturation Inter-Nuclear Kinetics), selectively saturates the magnetization of a minor spectral component with a series of rotor-synchronized DANTE pulse trains and monitors spin diffusion to other peaks with a non-selective 90° pulse. We have used SINK with ¹⁹F MAS NMR on samples of calcium fluorapatite doped with Sb³⁺ to measure spin diffusion between a weak peak at 68.6 ppm due to fluoride ions associated with Sb³⁺ and other peaks in the spectrum. The SINK experiment clearly demonstrates that spin diffusion from the former peak to the main resonance of fluorapatite at 64.0 ppm is faster than spin diffusion to a second antimony-related peak at 65.6 ppm. These results strengthen our previous conclusion that antimony(III) occupies a phosphate site in the apatite lattice, with an SbO₃³⁻ group replacing a PO₄³⁻ group. The SINK experiment also enables the detection of a “hidden” peak at approximately 62.9 ppm that is otherwise obscured by the intense main peak at 64.0 ppm.     

The resonance peak in the high-Tc cuprates

I present a theory in which the resonance peak observed in inelastic neutron scattering experiments on YBa₂Cu₃O_6+x and Bi₂Sr₂CaCu₂O_8+x arises from a dispersing spin mode. I argue that it is heavily damped in the normal state and becomes visible in the superconducting state due to a drastic decrease in the spin damping. I show that a spin-fermion model correctly describes the doping dependence of the peak position and of its integrated intensity. Finally, I derive a criterion for the existence of the resonance peak in other cuprate superconductors.     

Thermal studies of the spin liquid state and analog to the He melting curve in a geometrically frustrated magnet

Gadolinium gallium garnet, Gd₃Ga₅O₁₂ (GGG) has an extraordinary low-temperature phase diagram. Although the Curie–Weiss temperature of GGG is −2 K, GGG shows no long-range order down to T0.4 K. At low temperatures GGG has a spin glass phase at low fields (0.1 T), a field-induced long-range ordered antiferromagnetic state at fields of between 0.7 and 1.3 T, and, at intermediate fields, an apparent spin-liquid state without long-range order. We have characterized the intermediate field (IF) state through heat capacity, thermal conductivity, and magnetocaloric measurements. Our results show a sharp high-field phase boundary of the thermal irreversibility of the spin glass phase of GGG implying that the intermediate field phase is distinct from the spin glass. The lower field boundary of the AFM phase is shown to have distinct minimum at T0.2 K, in analogy to the minimum in the melting curve of ⁴He. The existence of such a minimum is confirmed by measurements of the latent heat of the transition below that temperature.     

Heteroepitaxial growth of high-temperature superconductors and doped manganites in ramp type geometry

We have studied heteroepitaxially grown ramp type structures consisting of high-temperature superconductors (HTS) and doped manganites in various configurations. Firstly, the coupling of two HTS electrodes via doped manganite barriers was analyzed and secondly the interface properties between HTS and doped manganites as well as between doped manganites with different Curie temperatures have been investigated. As a common feature of the interfaces involving doped manganites an increase in resistance at low temperatures was found which appears together with non-linear current–voltage characteristics. On applying external magnetic fields up to 8 T, the low temperature interface resistance is suppressed considerably. These observations can be understood in terms of a spin glass behavior of the doped manganites just at the interface caused by strain due to lattice misfit and disorder. The differential conductance spectra of YBa₂Cu₃O_7−δ–La_2/3Ca_1/3MnO₃ junctions with low transparency show a pronounced gap feature but no zero-bias conductance peak.     

掺Yb3+石英玻璃中非桥氧空穴缺陷特性的研究

为了对存在于石英玻璃中的非桥氧空穴缺陷的特性进行研究,采用高频等离子体法对掺Yb³⁺石英玻璃进行了制备。首先介绍了玻璃样品的制备过程,然后对所制备的掺Yb³⁺石英玻璃样品的吸收特性、发射特性以及傅里叶变换红外吸收光谱进行了分析。结果表明,所制备的玻璃样品具有Yb³⁺离子典型的吸收特性。位于260 nm波长的吸收峰以及200 nm激发波长下产生的位于630 nm波长的发射峰都表明所制备的玻璃样品中存在非桥氧空穴缺陷。并且不同激发波长所产生的发射峰以及红外吸收光谱都说明玻璃样品中的非桥氧空穴缺陷是由≡Si－O↑和≡Si－O↑…H－O－Si≡两类空穴中心构成,Yb³⁺离子对合作发光与非桥氧空穴缺陷间存在能量转移过程。     

Er3+掺杂硫系玻璃微球在980nm激光泵浦下的荧光特性

采用玻璃粉料高温漂浮熔融法制备了0.9%Er₂S₃（质量分数）：75%GeS₂-15%Ga₂S₃-10%CsI（摩尔分数）硫系玻璃微球,并用熔融拉锥法制备了锥腰直径为2.31 μm的石英光纤锥。将其与直径119 μm的硫系微球进行耦合,在980 nm 激光泵浦下获得了微球中与Er³⁺：⁴I_13/2→⁴I_15/2跃迁对应的1.54 μm处的荧光光谱。分析了微球和块状玻璃荧光光谱差异的原因,并用Mie散射理论公式对微球荧光光谱共振峰间隔进行了计算。共振峰间隔实验结果与理论计算误差最小仅为0.05%,验证了理论分析的正确性。最后,讨论了微球峰值间隔与泵浦功率的关系,排除了泵浦功率对共振峰间隔的影响。     

HOW DO THE EXCHANGE FLUCTUATIONS MAKE MAGNETIZATION TO BE ZERO IN SPIN GLASS STATE

In this note we calculate the lowest energy level as a function of the magnetization (m) for the spin glass s tate and find it increasing with m. We point out that this increase is the intrinsic reason for m being zero in spin glasses, even with average exchange (J₀)being a positive one.     

Study of structural and magnetic properties of Fe_(80)P-_9B_(11) amorphous alloy by ab initio molecular dynamic simulation

The structural and magnetic properties of Fe_(80)P_9B_(11) amorphous alloy are investigated through ab initio molecular dynamic simulation. The structure evolution of Fe_(80)P_9B_(11) amorphous alloy can be described in the framework of topological fluctuation theory, and the fluctuation of atomic hydrostatic stress gradually decreases upon cooling. The left sub peak of the second peak of Fe–B partial pair distribution functions(PDFs) becomes pronounced below the glass transition temperature, which may be the major reason why B promotes the glass formation ability significantly. The magnetization mainly originates from Fe 3d states, while small contribution results from metalloid elements P and B. This work may be helpful for developing Fe-based metallic glasses with both high saturation flux density and glass formation ability.     

丙硅乳液的核磁共振研究

单介绍了²⁹Si NMR实验技术;用²⁹Si NMR测定了丙硅乳液原料羟基硅氧烷的平均聚合度、平均分子量、平均羟基含量;用¹³C NMR分析了丙硅乳液的结构组成。     

旋涂法制备氧化锆介质层及其在薄膜晶体管中的应用

采用旋涂法制备了氧化锆介质层薄膜,重点讨论了退火温度以及旋涂转速对薄膜性能的影响及作用机制。研究发现高温后退火一方面使得氧化锆水合物脱水形成氧化锆,另一方面促使氧化锆薄膜结晶。此外,转速较高时,其变化对薄膜厚度及粗糙度无显著影响。当转速为5 000 r/min、退火温度为300℃时,制备的绝缘层厚度具有良好的厚度均匀性,粗糙度为0.7 nm,漏电流为3.13×10^-5 A/cm²（电场强度1 MV/cm）。最终,利用ZrO₂薄膜作为栅极绝缘层,在玻璃基板上制备了铟镓锌氧化物-薄膜晶体管（IGZO-TFT）,其迁移率为6.5 cm²/（V·s）,开关比为2×10⁴。