Modulated optical reflectance measurements on La2∕3Sr1∕3MnO3 thin films

Abstract

The modulated optical reflectance (MOR) measurement technique was applied to colossal magnetoresistive materials, in particular, La 2/3 Sr 1/3 MnO 3 (LSMO) thin films. The contactless measurement scheme is prospective for many applications spanning from materials characterization to new devices like reading heads for magnetically recorded media.A contrasted room temperature surface scan of a 100 µm wide 400 µm long bridge patterned into LSMO film provided preliminary information about the film homogeneity. Then the temperature was varied between 240 and 400 K, i.e. through the ferromagnetic to paramagnetic transition. A clear relation between the MOR signal measured as function of the temperature and the relative derivative of the resistivity up to the Curie temperature was observed. This relationship is fundamental for the MOR technique and its mechanism was explored in the particular case of LSMO. Analysis in the framework of the Drude model showed that, within certain conditions, the measured MOR signal changes are correlated to changes in the charge carrier concentration.2

Half-metallicity in a \chem{BiFeO_3/La_{\frac{2}{3}}Sr_{\frac{1}{3}}MnO_3} superlattice: A first-principles study

“…For the minority spin states, both R(ω) and Im( ) exhibit a band gap, reflecting the half-metallic character of LSMO. The spin majority reflectivity peak at 2 eV is consistent with the experimental peak with respect to energy and magnitude [41,42]. It is due to transitions from the hybridized O p and Mn d states into the Mn d states in the conduction band.…”

Investigation of ferromagnetic properties of LSMO nanolayers by laser modulated reflectance probe

“…The relative difference of reflectance of the film-substrate interface is of 0,0035 at 300 K for unmodulated light. The unmodulated absolute reflectance R (0,13 at 300 K) of the sample surface at the wavelength of the He-Ne laser (632,8 nm) is a function of temperature in good agreement with the values reported in references 8,12 for LSMO single crystals. The temperature profile of reflectance exhibits relative increase with a maximal value around Curie point and successive decrease in the paramagnetic phase.…”

“…8 ) to the relative change of carrier density. We assume thermal character of modulated reflectance, which excludes generation of free carriers by the pump laser radiation.…”

“…The obtained results validate the method for structural and defectoscopic analysis of LSMO manganites. A suggested application of a similar MOR scheme could be to read information from magnetically recorded media, where magnetization of the media will be sensed by the local change in the magnetic resistance 8 . The present investigation is accomplished as part of the collective research that facilitates the prospective development of a new range of electronic magnetoresistive devices.…”