The particle size and magnetic properties of charge-ordered (CO) Sm_0.5Ca_0.5MnO₃ (SCMO) manganites prepared by solid-state reaction with ball milling have been investigated. Studies on surface morphology and particle size show that the particle size of SCMO manganite without ball milling is relative large (about 4 μm). With the ball milling, the particles begin to disperse, the particle size gradually decreases, and it reaches hundreds to tens of nanometers after milling for 12 h to 36 h. At this time, the particles agglomerate. Magnetization versus temperature (M–T) measurements and the inverse susceptibility versus temperature (χ⁻¹–T) measurements show ferromagnetic (FM) transition at Curie temperature (T_C) and spin glass (SG) state at freezing temperature (T_f). Moreover, there is a bulging (sunken) peak near 273 K in the M–T (χ⁻¹–T) curves, suggesting that the CO anti-ferromagnetic (AFM) phase appears in the SCMO. The temperature corresponding to this bulging (sunken) peak represents CO temperature (T_CO). The results of magnetization versus field (M–H) loops, M–T curves and χ⁻¹–T curves show that the decrease of particle size with ball milling can suppress the formation of CO-AFM phase, decreasing the T_f, T_C, T_CO and coercive field (H_C). Our work shows that it is a way to tune SG state and Curie temperature by controlling the particle size of the manganites with charge ordering.

研究了通过球磨固态反应制备的电荷有序 (CO) Sm _0.5 Ca _0.5 MnO ₃ (SCMO) 锰酸盐的粒径和磁性能。表面形貌和粒径的研究表明，未经球磨的SCMO锰矿的粒径较大（约4μm）。随着球磨，颗粒开始分散，粒径逐渐减小，球磨12～36h后达到数百至数十纳米。此时，颗粒聚集。磁化与温度（M-T）的测量和逆磁化率对温度（χ ^-1 -T）的测量显示在居里温度铁磁（FM）过渡（Ť _Ç) 和在冷冻温度 ( T _f )下的自旋玻璃 (SG) 状态。此外，在 M-T (χ ^-1 -T) 曲线中在 273 K 附近有一个凸出（凹陷）峰，表明 CO 反铁磁（AFM）相出现在 SCMO 中。对应于该凸出（下沉）峰的温度代表 CO 温度（T _CO）。磁化强度与磁场 (M-H) 环、M-T 曲线和 χ ^-1 -T 曲线的结果表明，球磨过程中粒径的减小可以抑制 CO-AFM 相的形成，从而降低T _f , T _C , T _CO和矫顽场 ( H _C）。我们的工作表明，这是一种通过电荷排序控制锰酸盐的粒径来调节 SG 状态和居里温度的方法。