Temperature dependence of ferromagnetic resonance (FMR) frequency fFMR was revealed in Z-type hexaferrite (BaxSr1−x)3Co2Fe24O41 using microwave spectroscopy in zero external magnetic field. A linear decrease in fFMR toward magnetic phase transition temperature Tc2 = 500 K was observed, implicating magnetic anisotropy decrease. Ferromagnetic resonance studies performed near 9 GHz with the magnetic field up to 10 kOe also confirmed FMR anomaly near 500 K, where the magnetic structure changes from conical to collinear. FMR spectra are tunable by external dc and ac (100 kHz) electric fields which allowed us to determine the value of magnetoelectric coefficient αE = 390 ps/m at 170 K. αE is at about 0.5 kOe one order of magnitude lower than the reported value at 10 K, because in our case the electric field was applied along c-axis, while the previously reported value was obtained with the field in hexagonal plane. Nevertheless, our αE is still one or even four orders of magnitude higher than in other “high-temperature” multiferroics.

中文翻译：

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通过电场调制磁共振研究揭示多铁性 Z 型六铁氧体中的磁电耦合

铁磁共振 (FMR) 频率 fFMR 的温度依赖性在 Z 型六铁氧体 (BaxSr1-x)3Co2Fe24O41 中使用微波光谱在零外部磁场中揭示。观察到 fFMR 向磁相变温度 Tc2 = 500 K 线性降低，这意味着磁各向异性降低。铁磁共振研究在 9 GHz 附近进行，磁场高达 10 kOe，也证实了 500 K 附近的 FMR 异常，其中磁结构从锥形变为共线。FMR 谱可通过外部直流和交流 (100 kHz) 电场进行调谐，这使我们能够确定 170 K 时的磁电系数 αE = 390 ps/m。αE 约为 0.5 kOe，比报告值低一个数量级在 10 K 时，因为在我们的例子中电场沿 c 轴施加，而先前报告的值是在六边形平面中获得的。尽管如此，我们的 αE 仍然比其他“高温”多铁性材料高出一个甚至四个数量级。