Chemical pressure effect and anomalous critical behaviors of new type of diluted magnetic semiconductors with independently charge and spin doping

Zheng Deng; Shuang Yu; Guoqiang Zhao; Xiancheng Wang; Y. J. Uemura; Changqing Jin

doi:10.1117/12.2570667

21 August 2020 Chemical pressure effect and anomalous critical behaviors of new type of diluted magnetic semiconductors with independently charge and spin doping

Zheng Deng, Shuang Yu, Guoqiang Zhao, Xiancheng Wang, Y. J. Uemura, Changqing Jin

Author Affiliations +

Proceedings Volume 11470, Spintronics XIII; 114700Q (2020) https://doi.org/10.1117/12.2570667
Event: SPIE Nanoscience + Engineering, 2020, Online Only

Abstract

Chemical pressure is an effective method to tune physical properties, particularly for diluted magnetic semiconductors (DMS) of which ferromagnetic ordering is mediated by charge carriers. Via substitution of smaller Ca for larger Sr, we introduce chemical pressure on (Sr,Na)(Cd,Mn)2As2 to fabricate a new DMS material (Ca,Na)(Cd,Mn)2As2. Carriers and spins are introduced by substitutions of (Ca,Na) and (Cd,Mn) respectively. The unit cell volume reduces by 6.2% after complete substitution of Ca for Sr, suggesting a subsistent chemical pressure. Importantly the local geometry of [Cd/MnAs4] tetrahedron is optimized via chemical compression that increases the Mn-As hybridization leading to enhanced ferromagnetic interactions. As a result, the maximum Curie temperature (TC) is increased by about 50% while the the maximum saturation moment increases by over 100% from (Ca,Na)(Cd,Mn)2As2 to (Sr,Na)(Cd,Mn)2As2. We also successful synthesized (Ca,Na)(Zn,Mn)2Sb2 as a new DMS. This feature of independently charge and spin doping allows us to separately investigate the effect of carriers and of spins on the ferromagnetic properties of this new DMS alloy, and particularly of its critical ferromagnetic behavior.[1-8] We use modified Arrott plot analysis to establish critical exponents b, g, and d for this alloy. We find that at low Mn concentrations (< 10 at.%), it is governed by short-range 3D-Ising behavior, with experimental values of b, g, and d very close to theoretical 3D-Ising values of 0.325, 1.24, and 4.815. However, as the Mn concentration increases, this DMS material exhibits a mixed-phase behavior, with g retaining its 3D-Ising characteristics, but b crossing over to longer-range mean-field behavior.

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Zheng Deng, Shuang Yu, Guoqiang Zhao, Xiancheng Wang, Y. J. Uemura, and Changqing Jin "Chemical pressure effect and anomalous critical behaviors of new type of diluted magnetic semiconductors with independently charge and spin doping", Proc. SPIE 11470, Spintronics XIII, 114700Q (21 August 2020); https://doi.org/10.1117/12.2570667

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KEYWORDS

Doping

Magnetic semiconductors

Ferromagnetics

Calcium

Manganese

Strontium

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