Thermomagnetic switching in strong/weak/strong ferromagnet stack detected with resonant X-ray magnetic reflectometry

摘要

It is of interest to explore magnetic configurations and phase transitions at the interfaces between different magnetic materials by employing nondestructive and element-specific methods such as resonant X-ray magnetic reflectometry (RXMR). Using RXMR, we have measured element-specific hysteresis loops of a layered stack of TaO(15nm)/Ir_(20)Mn_(80)(25nm)/Co_(90)Fe_(10)(3nm)/Ni_(67)CU_(33)(10nm)/Ni_(80)Fe_(20)(10nm)/quartz substrate at the Fe h Ni absorption edges. The goal here is to highlight the contribution of the weakly ferromagnetic Ni_(67)Cu_(33) spacer in this system where the spacer is sandwiched between strong ferromagnets, Ni_(80)Fe_(20) and Co_(90)Fe_(10). We find two kinds of the spacer effects on magnetization switching in the system. One of them is that switching of the Co_(90)Fe_(10) magnetization displays at the Ni absorption edge. Such a behavior of the magnetic reflectivity results from strong exchange coupling of the spacer to the Co_(90)Fe_(10) surrounding across the interface between them. Another one is that temperature variation around the Curie point of the spacer (T_c ≈ 240 K) provides a stronger change of the magnetic contrast at the Ni_(80)Fe_(20)/Ni_(67)Cu_(33) interface than that at the Co_(90)Fe_(10)/Ni_(67)Cu_(33) one. This feature indicates weaker exchange coupling across the Ni_(80)Fe_(20)/Ni_(67)Cu_(33) interface.