Influence of Technologically Driven Disorder on Spin Dynamics in ${\rm La}_{0.9}{\rm Ca}_{0.1}{\rm MnO}_{3}$ Manganites in Mid-to-Far Critical Range

Abstract

Electron paramagnetic resonance measurements were used to probe spin dynamics over mid-to-far critical range for four samples of different structural forms of La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.9</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . As a result of different fabrication routes, these samples contain different imperfections which may have specific impacts on temperature dependence of the EPR linewidth. An analysis of critical spin relaxation speedup, manifested by sharp increase of the linewidth and Onsager kinetic coefficient when approaching to magnetic transition points, was carried out using two critical exponents derived from dynamic and static scaling laws. Deviations of these exponents from theoretical bounds were proposed to be hallmarks of the disorder types.