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Stable long-range magnetic order in low-dimensional semiconductors up to room temperature has long been the pursuit of researchers for their potential applications in the field of spintronic and memory devices. However it is a great challenge to achieve magnetic phase transition together with a controllable band structure in two-dimensional magnetic materials simultaneously. Through fully terminated oxygen group adsorption, the transformation from ferromagnetic metal to antiferromagnetic semiconductor with a high Neél temperature (425 K) has been achieved in Cr 2 B 2 MBene, which is attributed to superexchange interaction between the interlayer magnetic chromium (Cr) atoms. Furthermore, exotic quantum phase transition between two different antiferromagnetic states of Cr 2 B 2 O 2 , together with the transition from semiconductor to metal, is observed when applying compressive strain. Interestingly, ferromagnetic half-metal and ferromagnetic semiconductor states are achieved by nonuniform oxygen group adsorption, resulting from electrical potential difference between the Cr atomic layers and thus built-in electric field. Our results reveal the origin of magnetic phase transition in Cr 2 B 2 MBene and offer a new avenue to obtain magnetic multifunctional materials for spintronic devices.

Abstract. With the development of society, people's requirements on the comfort of environment have been further improved. The semiconductor refrigeration technology, with the increase of material merit, has been greatly developed and widely used in civil and military fields. This paper, starting from the Peltier effect, first of all analyzes the influence of optimal coefficient and temperature difference on semiconductor refrigeration system in two kinds of extreme conditions. In addition, the curves of various factors on the semiconductor refrigeration are determined, which intuitively reflect the effects of various factors on the semiconductor refrigeration and their relationship. Secondly, based on the simulation results of the thermodynamic model, the impact of various factors on the semiconductor refrigeration system is simulated and the temperature change in a small range of space is determined. What's more, the impacts of various factors on the semiconductor refrigeration is summed up, and optimized suggestions are put forward. The study results showed that the performance of semiconductor refrigeration system is influenced by many factors. Through the study of effects of various factors on the semiconductor refrigeration, the temperature changes of semiconductor refrigeration in space are simulated, which can provide technical support for the development of semiconductor system.

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