Giant Room Temperature Magnetoimpedance in La_0.7Ba_0.15Sr_0.15MnO₃ and Development of a Sensitive Position Detector

Observation of room temperature giant magnetoimpedance in La_0.7Ba_0.15Sr_0.15MnO₃ compound having nanometric grain size is reported under low magnetic field and over the frequency range between 50 KHz and 15 MHz. Both the resistive and reactive components of impedance increase with increasing frequency due to skin effect of the metallic state below T _C. Above a critical frequency (1 MHz), a sharp increase in both R and X and hence Z is observed. The applied magnetic field influences the impedance by affecting the penetration depth via the transverse permeability and gives rise to large magnetoimpedance (∼70%) at low fields up to 0.1 T. Magnetoimpedance of La_0.7Ba_0.15Sr_0.15MnO₃ compound display major change (∼61%) between 0.02 and 0.035 T and appears to originate due to the spin alignment of the charge carriers across the grain boundaries. At fields >0.1 T, magnetoimpedance displays near saturation, corresponding to the completion of the spin alignment across the grain boundaries. An unique scaling behavior has been observed for field dependence of magnetoimpedance at various frequencies, which could be well accounted by a phenomenological model. Feasibility of the development of a sensitive linear position sensor is also demonstrated.