Mössbauer magnetic scans: basic principles, experimental layout and data analysis

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

La Plata, Argentina

Conferencia; Latin American Conference on the Applications of the Mössbauer Effect; 2008

Mossbauer Magnetic Scans (MMS) allows to study the response of magnetic momentsto an external applied eld. In the case of ferromagnetic samples, studies of domaindynamics can be performed. The important advantage oered by the MMS methodologyin comparison with conventional techniques is that responses from dierent phases orsites can be distinguished. MMS are performed by precisely selecting Doppler velocitieswith a constant velocity drive [1], and measuring the transmission rate while a magneticexternal eld is modulated. A multiescaler is used, synchronically with the exciting aceld, to record enough magnetic sweeps as to attain the required statistics.To understand the patterns observed in previously MMS [2] and dene an analysismethodology, two -Fe samples are studied, with thicknesses of 12 m less and of lessthan 1 m.The thin absorber results can be analysed within the well known thin absorber approach.For the thicker one, both polarization and thickness eects must be taken intoaccount. However, more information can be retrieved in the second case. For thin absorbers,only the eld dependence of the mean square projection (MSP) of the magneticmoments in the gamma rays direction is obtained. For thick samples, the asymetry onthe MSP over the plane orthogonal to the gamma direction is also obtained.For the 12m -Fe sample, the MSP along the gamma ray direction and the MSPasymmetry in the orthogonal plane, are presented as quasi-continuous functions of theapplied eld for a complete quasi-static magnetic cycle. It is shown that MSP goes slowerto saturation in the sample plane than in its normal direction, reecting the magneticshape anysotropy of the sample.The MMS experimental layout and experimental details are also presented.[1] A. Veiga, N. Martnez, P. Mendoza Zelis, G. A. Pasquevich, F. H. Sanchez, "Advancesin constant-velocity Mossbauer instrumentation", Hyperne Interact. 167 (2006),pp 905.[2] G.A. Pasquevich, P. Mendoza Zelis, F.H. Sanchez, M.B. Fernandez van Raap, A.L.Veiga, N. Martinez, "Determination of the iron atomic magnetic moments dynamics inthe nanocrystalline ribbons Fe90Zr7B3 by Mossbauer magnetic scans" , Physica B, 384(2006), pp 348.Email: gpasquev@sica.unlp.edu.arKeywords: Magnetic Mossbauer Scan, Constant velocity, Polarization eect, Magneticdynamic