Local Magnetic Susceptibility by Mossbauer Effect

G. A. PASQUEVICH; P. MENDOZA ZÉLIS; N. MARTÍNEZ; A. VEIGA; M. B. FERNÁNDEZ VAN RAAP; F. H. SÁNCHEZ

Lima

Conferencia; LACAME10, XII Latin American Conference on the Applications of the Mössbauer Effect; 2010

Classical Mossbauer spectroscopy has been widely expanded to Mossbauer scans on temperature and on magnetic field. In the latter it was demonstrated the ability of the Mossbauer magnetic scans (MMS) to give a cuasi-continuous dependence of the magnetic moments orientations with the applied field. In that way the information so obtained is related with the one obtained by a B vs H cycle, with the additional advantages of Mossbauer Effect and its spectroscopy, like the local character and the ability to distinguish different phases or sites and so measure the corresponding magnetic response independently. In the present work a new application of this M¨ossbauer operation mode is presented. The M¨ossbauer Effect is synchronically recorded with an applied field consisting of a DC component (up to 100 Oe) and a small AC component (up to 10 Oe) with frequency in the order range of the few kHz. The energy of the gamma photons is chosen to match one of the absorption lines of the Mossbauer magnetic spectrum. The so obtained results may be considered related and complementary to magnetic AC susceptibility. For low AC magnetic field amplitudes, at which the response may be considered lineal, amplitude and phase shift of the M¨ossbauer Effect variations relative to the excitation field may be recorded as a function of frequency. The former may provide information on magnetic moments spatial variations, while the latter gives information on characteristic times of these variations. Here the experimental set up, acquisition mode, and preliminary considerations on data analysis and interpretation are discussed. The experiments were performed on a 20 μm Fe78B13Si9 ribbon, obtained by melt-spinning over which 20 μm Al film was grown by sputtering on both faces [3]. A delay from 0 to 0.037¼ as excitation frequency changes from 0 to 2 kHz, which is independent of DC applied field, is reported. The plausibility to study systems displaying dynamic with more noticeable frequency dependence is discussed.