Room-Temperature Electric-Field Controlled Ferromagnetism in Mn0.05Ge0.95 Quantum Dots

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• 作者：Faxian Xiu ; Yong Wang ; Jiyoung Kim ; Pramey Upadhyaya ; Yi Zhou ; Xufeng Kou ; Wei Han ; R. K. Kawakami ; Jin Zou ; Kang L. Wang
• 刊名：ACS Nano
• 出版年：2010
• 出版时间：August 24, 2010
• 年：2010
• 卷：4
• 期：8
• 页码：4948-4954
• 全文大小：533K
• 年卷期：0
• ISSN：1936-086X

文摘

Room-temperature control of ferromagnetism by electric fields in magnetic semiconductors has been actively pursued as one of important approaches to realize practical spintronic and nonvolatile logic devices. While Mn-doped III−V semiconductors were considered as potential candidates for achieving this controllability, the search for an ideal material with high Curie temperature (T_c > 300 K) and controllable ferromagnetism at room temperature has continued for nearly a decade. Recently, Mn_0.05Ge_0.95 quantum dots (QDs) were demonstrated to have a T_c above 300 K. However, the field control of ferromagnetism based on hole-mediated effect remained at low temperatures and thus prohibited spintronic devices operable at ambient environment. Here, we report a successful demonstration of electric-field control of ferromagnetism in the Mn_0.05Ge_0.95 quantum dots up to 300 K. We show that, by using quantum structure, high-quality material can be obtained and effective hole mediation due to quantum confinement effect can be achieved. Upon the application of gate bias to a metal-oxide-semiconductor (MOS) capacitor, the ferromagnetism of the channel layer, that is, the Mn_0.05Ge_0.95 quantum dots, was manipulated through the change of hole concentration. Our results are fundamentally and technologically important toward the realization of room-temperature spin field-effect transistors and nonvolatile spin logic devices.