Modulated optical reflectance measurements on La 2 ∕ 3 Sr 1 ∕ 3 Mn O 3 thin films

• Published in: Journal of applied physics 2005-11, Vol.98 (10), p.103902-103902-7
• Main Authors: Méchin, Laurence, Flament, Stéphane, Perry, Andy, Almond, Darryl P., Chakalov, Radoslav A.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2128693

The modulated optical reflectance (MOR) measurement technique was applied to colossal magnetoresistive materials, in particular, La 2 ∕ 3 Sr 1 ∕ 3 Mn O 3 (LSMO) thin films. The contactless measurement scheme is prospective for many applications spanning from materials' characterization to devices such as reading heads for magnetically recorded media. A contrasted room-temperature surface scan of a 100 - μ m -wide and 400 - μ m -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 a 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 the changes in the charge-carrier concentration.