The central shift of 57Fe atoms with trapped interstitials (mixed dumbbells) in aluminium increases steeply at temperatures between 10 and 20 K. Influences of restricted diffusion of the Mossbauer atom in a cage on the isomer shift and second order Doppler shift are discussed.

We have analysed in terms of static hyperfine field distributions the Mossbauer spectra of mixed Zn-Mg ferrites. Typical features of semi-spin glasses are observed both in average and locally: in each sample, the relevant data are smeared out in a way which reveals the behavior of the series.

A previously undescribed magnetotactic spirillum isolated from a freshwater swamp was mass cultured in the magnetic as well as the nonmagnetic state in chemically defined culture media. Results of Mossbauer spectroscopic analysis applied to whole cells identifies magnetite as a constituent of these magnetic bacteria.

Mossbauer spectroscopy of the synthetic tetramers [Fe4S4(SR)4]2(R = alkyl, aryl) and the corresponding trianions obtained by one-electron reduction, when compared with available data for 4-Fe and 8-Fe iron-sulfur proteins, shows that these tetramers are electronic analogs of the active sites of the proteins.

The conversion of magnetite to maghemite has been studied kinetically in the ultrafine particle range (77-220A) by chemical analysis. X-ray diffraction, and Mossbauer measurements. The reaction is third order. The activation temperatures are relatively low (8 250-1 1 200 K). Electron hopping in ultrafine magnetite powders is discussed on the basis of the results.

~ong the easy axis a at 4.2 K induces phase transi­ tionsatHI =39 kOe andH2 =46 kOe [1-3]. In this ~t1er we report the use of Mossbauer spectroscopy in external magnetic fields to study the magnetic struc­ (ure of each of the three phases. Previous Mossbauer work in FeCI2 · 2HZ0 includes apower study by Chandra and Hoy [4] and a single z crystal study by Johnson [5]. They found a magnetic o hyp...

MGssbauer experiments using the 86.5 keV resonance of 1 5 5 ~ d have been performed on Gdl+,Fe4B4 with and without substitution of 20 % of Gd by Nd or Sm. All these alloys are characterized by a very large quadrupolar interaction. At T = 4.2 K, i.e. below the magnetic temperature order, the Miissbauer spectra are quite different for the three alloys, owing to the different direction of the Gd m...

Two systems of nanoparticles with different surface states have been prepared by sol-gel methods and analysed by X-ray diffractometry, transmission electron microscopy, thermal analysis and temperature dependent Mossbauer spectroscopy. Surface states and phase content, particle mean size and the magnetic anisotropy energy constant were evaluated.