Magnetization dynamics in La0.67Ca0.33MnO3 epitaxial films probed with resonant and non-resonant microwave absorption

Abstract

Exchange bias effect in epitaxial La0.67Ca0.33MnO3/SrMnO3 thin film structure J. Appl. Phys. 116, 083908 (2014) Temperature (T) dependent microwave absorption measurements are performed on La 0.67 Ca 0.33 MnO 3 (LCMO) epitaxial thin films of thickness 100 and 200 nm in an electron paramagnetic resonance spectrometer operating in X-band. The resonant absorption peak is monitored for out-of-plane (H ? ) and in-plane (H k ) dc magnetic field (H) as the system goes through magnetic ordering. These data suggest a resilient transformation to the ferromagnetic (FM) phase in the vicinity of the Curie temperature (T C ), indicative of a phase separation, which is dominant in the thinner film. The saturation magnetization is calculated from SQUID magnetometry on the same film. A pronounced zero-field absorption is seen in H k geometry displaying anomalous growth in 100 nm film at T < T C . This feature is correlated with the magneto-conductivity of the manganite which is colossal in the vicinity of T C in the well-ordered film of thickness 200 nm. Signature of standing spin wave modes is seen in H ? measurements which are analyzed to calculate the spin wave stiffness constant D(T) in the limit of zero temperature. The same is also inferred from the decay of equilibrium magnetization in the framework of Bloch law. These studies reveal that a bulk like LCMO is obtained in the fully relaxed thicker films. V C 2015 AIP Publishing LLC.

Mechanisms of AC losses in magnetic fluids based on substituted manganites

“…Along with traditionally considered processes of Neel-Brown relaxation and remagnetization based on Stoner-Wohlfarth model, 10,23,30,31,32,33 there are also ideas that due to significant magnetoresistance effects in the vicinity of the Curie point, eddy currents should be taken into account as a part of the heating mechanism. [34][35][36] It is also unclear how the relative contributions of the above mechanisms depend on MNP parameters and external factors (amplitude H max and frequency f of AMF). A traditional way to study the AC losses in MNPs is to extract necessary parameters of MNPs from magnetostatic measurements and use them to model remagnetization processes and calculate SLP values.…”