Linearly shifting ferromagnetic resonance response of La_0.7Sr_0.3MnO₃ thin film for body temperature sensors

Human body temperature not only reflects vital signs, but also affects the state of various organs through blood circulation, and even affects lifespan. Here a wireless body temperature detection scheme was presented that the temperature was extracted by investigating the out-of-plane (OP) ferromagnetic resonance (FMR) field of 10.2 nm thick La_0.7Sr_0.3MnO₃ (LSMO) film using electron paramagnetic resonance (EPR) technique. Within the range of 34–42 °C, the OP FMR field changes linearly with the increasing or decreasing temperature, and this variation comes from the linear responses of magnetization to the fluctuant temperature. Using this method, a tiny temperature change (< 0.1 °C) of organisms can be detected accurately and sensitively, which shows great potential in body temperature monitoring for humans and mammals.