Electric field-controlled ferromagnetism of (Zn,Co)O is demonstrated via anomalous Hall effect measurements. The electron carrier concentration in this material is 1.65×1020 cm−3 as measured via ordinary Hall effect at 4 K, and an anomalous Hall effect is observed up to 6 K, but with no hysteresis at any temperature. With positive electric gate field, the carrier concentration is increased by approximately 2%, resulting in a clear magnetic hysteresis at 4 K. The ability to reversibly induce∕eliminate ferromagnetism by applied gate field alone, measured via the effect on the carriers, is a clear sign of carrier-induced ferromagnetism in this system.
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机译：通过异常霍尔效应测量证明了（Zn，Co）O的电场控制铁磁性。通过普通霍尔效应在4 K下测量，该材料中电子载流子浓度为1.65×10 20 cm −3 ，在6 K以下观察到异常的霍尔效应，但在任何温度下都没有滞后。在正的栅极电场下，载流子浓度增加了大约2％，在4 K时产生了清晰的磁滞。仅通过施加的栅极电场可逆地消除∕铁磁性的能力（通过对载流子的影响进行测量）是一种该系统中载流子引起的铁磁性的明显迹象。
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