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Cyclic Heating-Annealing and Boltzmann Distribution of Free Energies in a spin-glass System

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Communications in Theoretical Physics 2007年第7期48卷 179-182页

作者： ZHOU Hai-Jun Institute of Theoretical Physics,the Chinese Academy of Sciences,Beijing 100080,China Institute of Theoretical Physics the Chinese Academy of Sciences Beijing 100080 China

Ergodicity of a spin-glass is broken at low temperatures;the system is trapped in one of many ergodicconfigurational *** between different ergodic domains are achievable through a *** this experiment is repeated infinite times,all ergodic configurational domains will be visited with frequencesthat decreasing exponentially with their free *** mean free energy density of a spin-glass system on a randomgraph is calculated based on this free energy Boltzmann distribution in the present work,by means of the cavity approach.

关键词： spin-glass ergodicity-broken cavity method

Observation of spin-glass behavior in 1111-type magnetic semiconductor(La,Ba)(Zn,Mn)SbO

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Chinese Physics B 2023年第12期32卷 547-553页

作者：赵雪芹董金瓯张茹菲杨巧林谢玲凤傅立承顾轶伦潘洵宁凡龙 Zhejiang Province Key Laboratory of Quantum Technology and Device and School of Physics Zhejiang UniversityHangzhou 310027China State Key Laboratory of Silicon and Advanced Semiconductor Materials Zhejiang UniversityHangzhou 310027China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China Science and Technology Innovation Center Chifeng High-Tech Industrial Development ZoneChifeng 025250China

We report the successful fabrication of a new 1111-type bulk magnetic semiconductor(La,Ba)(Zn,Mn)SbO through the solid solution of(La,Ba)and(Zn,Mn)in the parent compound *** polycrystalline samples(La,Ba)(Zn,Mn)SbO crystallize into ZrCuSiAs-type tetragonal structure,which has the same structure as iron-based superconductor LaFeAsO_(1-δ).The DC magnetization measurements indicate the existence of spin-glass ordering,and the coercive field is up to~11500 Oe(1 Oe=79.5775 A·m^(-1)).The AC magnetic susceptibility further determines that the samples evolve into a conventional spin-glass ordering state below the spin freezing temperature T_(f).In addition,the negative magnetoresistance(MR≡[ρ(H)-ρ(0)]/ρ(0))reaches-88%under 9 T.

关键词： magnetic semiconductors spin-glass negative magnetoresistance

A New Parallel Algorithm for Simulation of spin-glass Systems on Scales of Space-Time Periods of an External Field

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Journal of Modern Physics 2011年第6期2卷 488-497页

作者： A. S. Gevorkyan H. G. Abajyan H. S. Sukiasyan 不详

We study the statistical properties of an ensemble of disordered 1D spatial spin-chains (SSCs) of certain length in the external field. On nodes of spin-chain lattice the recurrent equations and corresponding inequal-ity conditions are obtained for calculation of local minimum of a classical Hamiltonian. Using these equa-tions for simulation of a model of 1D spin-glass an original high-performance parallel algorithm is developed. Distributions of different parameters of unperturbed spin-glass are calculated. It is analytically proved and shown by numerical calculations that the distribution of the spin-spin interaction constant in the Heisenberg nearest-neighboring Hamiltonian model as opposed to the widely used Gauss-Edwards-Anderson distribu-tion satisfies the Lévy alpha-stable distribution law which does not have variance. We have studied critical properties of spin-glass depending on the external field amplitude and have shown that even at weak external fields in the system strong frustrations arise. It is shown that frustrations have a fractal character, they are self-similar and do not disappear at decreasing of calculations area scale. After averaging over the fractal structures the mean values of polarizations of the spin-glass on the scales of external field's space-time peri-ods are obtained. Similarly, Edwards-Anderson’s ordering parameter depending on the external field ampli-tude is calculated. It is shown that the mean values of polarizations and the ordering parameter depending on the external field demonstrate phase transitions of first-order.

关键词： spin-glass Hamiltonian Birkhoff Ergodic Hypothesis Statistic Distributions Frustration Fractal Parallel Algorithm Numerical Simulation

(Ba_(1−x)Na_(x))F(Zn_(1−x)Mn_(x))Sb: A novel fluoride-antimonide magnetic semiconductor with decoupled charge and spin doping

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Journal of Semiconductors 2022年第11期43卷 38-43页

作者： Xueqin Zhao Jinou Dong Licheng Fu Yilun Gu Rufei Zhang Qiaolin Yang Lingfeng Xie Yinsong Tang Fanlong Ning Zhejiang Province Key Laboratory of Quantum Technology and Device and Department of Physics Zhejiang UniversityHangzhou 310027China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China State Key Laboratory of Silicon Materials Zhejiang UniversityHangzhou 310027China

We report the successful synthesis and characterization of a novel 1111-type magnetic semiconductor(Ba_(1−x)Na_(x))F(Zn_(1−x)Mn_(x))Sb(0.05≤x≤0.175)with tetragonal ZrSiCuAs-type structure,which is isostructural to the layered iron-based superconductor La(O,F)*** substitutions for Ba and Mn substitutions for Zn introduce carriers and local magnetic moments,*** interaction is formed when Na and Mn are codoped,demonstrating that local magnetic moments are mediated by ***-thermal magnetization shows that the coercive field is as large as-12000 Oe,which is also reflected in the large split between the temperature-dependent magnetization in zero-field-cooling and field-cooling *** susceptibility under zero field demonstrates that samples evolve into spin-glass state below spin freezing temperature T_(f).The measurements of temperature-dependent resistivity indicate that(Ba_(1−x)Na_(x))F(Zn_(1−x)Mn_(x))Sb exhibits semiconducting behaviour.

关键词： magnetic semiconductors ferromagnetic interaction carriers spin-glass

Distribution of Equilibrium Free Energies in a Thermodynamic System with Broken Ergodicity

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Communications in Theoretical Physics 2008年第3期49卷 659-664页

作者： ZHOU Hai-Jun LI Kang Institute of Theoretical Physics the Chinese Academy of Sciences Beijing 100080 China

At low temperatures the configurational phase space of a macroscopic complex system （e.g., a spin-glass） of N - 10^23 interacting particles may split into an exponential number Ωs - exp（const × N） of ergodic sub-spaces （thermodynamic states）. It is usually assumed that the equilibrium collective behavior of such a system is determined by its ground thermodynamic states of the minimal free-energy density, and that the equilibrium free energies follow the distribution of exponentied decay. But actually for some complex systems, the equilibrium free-energy values may follow a Gaussian distribution within an intermediate temperature range, and consequently their equilibrium properties are contributed by excited thermodynamic states. Based on this analysis, the re-weighting parameter y in the cavity approach of spin-glasses is easily understood. Depending on the free-energy distribution, the optimal y can either be equal to or be strictly less than the inverse temperature β.

关键词： free-energy distribution spin-glass thermodynamic state cavity approach broken ergodicity