Mössbauer studies of hyperfine fields in disordered Fe2CrAl

Abstract

Heusler-like alloy Fe 2 CrAl was prepared and studied. Structure determination was done by X-ray. The structure was found to conform to the B 2 type. Magnetic hyperfine fields in this sample were studied by the Mössbauer effect. The Mössbauer spectra were recorded over a range of temperature from 40 to 296 K. The Mössbauer spectra showed the co-existence of a paramagnetic part with a magnetic hyperfine portion at all recorded temperatures. Even with the distribution in the magnetic hyperfine field, the average hyperfine field follows the´T T c µ 3 2 law. The paramagnetic part of the hyperfine field is explained in terms of the clustering of Cr atoms.

Mössbauer effect and magnetization studies of the Fe2+xCr1−xAl system in theL21(X2YZ) structure

“…As can be seen in table 1, in the ordered L2 1 phase the lattice parameter decreases slightly in the off-stoichiometric alloys. An earlier reported value for the L2 1 phase is a = 5.805 Å [6], whereas for the disordered B2 (sc) phase the reported value is 2a = 5.807 Å [5]. A satisfactory agreement exists between the results given in table 1 and those reported in the literature for the ordered phase.…”

“…Results of experiments with polarized radiation which have investigated the Fe 2p spectra of pure Fe have shown that the contributions of spin-up and spin-down electrons are different [4]. Fe 2 CrAl alloy has been prepared and studied in the disordered B2 (simple cubic, sc) phase [5]. Mössbauer spectroscopy studies have shown the coexistence of a paramagnetic part (which has been ascribed to clustering of Cr atoms) with a magnetic hyperfine portion at several temperatures between 40 and 296 K. The average hyperfine field B hf follows the (T /T C ) 3/2 law.…”

Evolution of ferromagneticlike order inFe2V1−xCrxAlHeusler alloys

“…Band-structure calculations predicted Fe 2 TiAl to exhibit anomalous electronic properties, but experimentally it was found to be metallic with a magnetic transition around 100 K. 20 On the other hand, Fe 2 CrAl stabilizes in single phase B2-type crystal structure possessing nonmetallic but ferromagnetic behavior with Curie temperature ͑T C ͒ of 246 K. 20,21 Contrary to these observations coexistence of paramagnetic and weak ferromagnetic components in the temperature range of 40-296 K has also been reported. 22 It was also observed that magnetic transition extends over a wider temperature range ͑T C = 330͒, disappearing with increasing magnetic field intensity, attributed to the clustering of Cr atoms, 22,23 formation of Fe clusters, 4 or presence of Cr clusters around Fe. 24 Although from electronic structure calculations Fe 2 CrAl system was predicted to be a half-metallic ferromagnet 25 ͑HMF͒ the experimental results showed nonmetallic character with higher density states at the Fermi level compared to Fe 2 VAl.…”

Comparative study of the structural and magnetic properties of bulk and nanostructured Fe2CrAl

“…The magnetic hyperfine field distribution for the bulk sample shows two high field components of almost equal intensity centred at 28.6 T and 19.8 T in addition to a low field component at 9.5 T. In the well-ordered L 21 Heusler structure, there are two crystallographically equivalent sites and so Fe at these sites would have the same environment with only one peak in the magnetic HFD [1]. The low field peak at 9.5 T can therefore be attributed to Fe atoms in the perfectly ordered environment.…”