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

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

La Plata, Argentina

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

Mssbauer Magnetic Scans (MMS) allows to study the response of magnetic moments to an external applied eld. In the case of ferromagnetic samples, studies of domain dynamics can be performed. The important advantage oered by the MMS methodology in comparison with conventional techniques is that responses from dierent phases or sites can be distinguished. MMS are performed by precisely selecting Doppler velocities with a constant velocity drive [1], and measuring the transmission rate while a magnetic external eld is modulated. A multiescaler is used, synchronically with the exciting ac eld, to record enough magnetic sweeps as to attain the required statistics. To understand the patterns observed in previously MMS [2] and dene an analysis methodology, two -Fe samples are studied, with thicknesses of 12 üm less and of less than 1um.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 into account. 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 magnetic moments in the gamma rays direction is obtained. For thick samples, the asymetry on the MSP over the plane orthogonal to the gamma direction is also obtained.For the 12um -Fe sample, the MSP along the gamma ray direction and the MSP asymmetry in the orthogonal plane, are presented as quasi-continuous functions of the applied eld for a complete quasi-static magnetic cycle. It is shown that MSP goes slower to saturation in the sample plane than in its normal direction, reflecting the magnetic shape anysotropy of the sample.The MMS experimental layout and experimental details are also presented.[1] A. Veiga, N. Martinez, P. Mendoza Zelis, G. A. Pasquevich, F. H. Sanchez, "Advancesin constant-velocity Mossbauer instrumentation", Hyperne 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.