G. Rajaram

Iron hyperfine field distribution in amorphous FeNiCrMoSiB

Abstract The distribution of Fe hyperfine fields, P ( H ), has been studied for the amorphous ferromagnetic alloys Fe 40− x 2 Ni 40− x 2 Cr x Mo 2 Si 10 B 8 , x = 0, 1, 3, 4, 5 by Mossbauer measurements at room temperature. The results favour a bimodal distribution for P ( H ) as suggested earlier for METGLAS 2826A. The low field component is found to increase with x .

Resistivity and longitudinal magnetoresistance studies in amorphous FeNiCrMoSiB

Abstract With a view to study the effect of Cr on the transport properties of FeNi based amorphous magnetic materials, electrical resistivity and magnetoresistance measurements have been carried out on α-Fe40-x/2Ni40-x/2CrxMo2Si10B8 (0

Low temperature resistivity studies in Cr containing amorphous alloys Fe-Ni-Cr-Mo-Si-B

Resistivity data on Fe 40-x/2 Ni 40-x/2 Cr x Mo 2 Si 10 B 8 samples with x = 0,1,3,4,5 in the temperature region 7 K - 300 K have been reported. A minimum is observed in the resistivity as a function of temperature at a temperature T min varying between 20 K to 80 K for the five samples. Attempts are made to fit the data with a sum of a T2term and various functional forms predicted for the negative temperature coefficient region.

Anisotropic spin glass behaviour of FeMnTiO5 system

Mössbauer effect, d.c. magnetisation (temperature variation, irreversibility, hysteresis and field dependence), a.c. susceptibility and x-ray measurements in FeMnTiO5 (4.2 ≤ T <- 500 K) show it to be an anisotropic reentrant ferrimagnet where magnetic ordering and spin freezing occur only along the c-axis. This is a consequence of the f- and c- site chemical disorder, and orthorhombic c-axis distortion.

Low temperature Mössbauer study of amorphous Fe-Ni-Cr-Mo-Si-B

Abstract Chromium containing amorphous alloys of composition Fe 40− x 2 Ni 40− x 2 Cr x Mo 2 Si 10 B 8 , x=0,1,3,4,5, have been studied by Mossbauer effect at 4.4 K. The results indicate that the large reductions in the saturation magnetisation observed in these alloys on addition of Cr may be largely due to the reduction of the Fe moment in the neighbourhood of Cr.

Mössbauer studies in a-Fe76-xNixCr4B12Si8

Room temperature Mössbauer studies on a-Fe76-xNixCr4B12Si8 alloys (0≤x≤30) are reported. The average hyperfine field is observed to remain constant. P(H) shows a low hyperfine field component which is found to be nearly absent for 2≤x≤4 samples. An attempt has been made to understand the correlation of this to the low temperature resistivity behaviour of Cr containing Fe-based amorphous alloys.

Remarkable change in resistivity minimum temperature in the presence of Ni in a-Fe-Cr-B-Si alloys

Resistivity studies have been carried out on a-Fe76−xCr4NixB12Si8 for x = 0, 5, 10, 20, 30 in the temperature range of 1.5 K to 300 K. It is found that the temperature at which resistivity shows a minimum (Tmin) is a strong function of Ni concentration. By the addition of 5 to 10 at % Ni, the change caused in Tmin by Cr is compensated, and its value is found to be ∼20 K similar to Fe80B12Si8 alloy.

Effect of Cr on hyperfine parameters in a-Fe-Cr-Si-B alloys

Mössbauer studies on a-Fe80−xCrxSi8B12 (x = 0,2,...12) at 5K have been reported. The average hyperfine field and width of P(H) distribution have been analysed by a model which assumes a random distribution of Cr atoms. On assumption that the hyperfine field distribution of Fe atom with r number of Cr nearest neighbours is given by a gaussian with a mean field Hr =Ho - rC1 + r2C2; C and C2 being constants; broad features of Mössbauer spectra are explained.

Temperature dependence of hyperfine parameters in Fe-Ni-Cr-Mo-Si-B

Abstract The temperature dependence of the average and width of the hyperfine field distribution, isomer shift and the intensity ratio I 2,5 / I 3,4 are reported for amorphous Fe 40- x /2 Ni 40- x /2 Cr x Mo 2 Si 10 B 8 , x = 0–5. The spin-wave constant, B , determined from the temperature dependence of the average hyperfine field is larger than that determined from net magnetization data for x = 5. The hyperfine field distribution in the crystallised alloys are reported.

Mossbauer studies in sputtered A-Fe 80 B 20 foils

Mossbauer studies have been carried out on sputtered amorphous Fe 80 B 20 foils in the temperature range of 4.4 K to 300 K. The results have been analysed using Windows method. The coefficients B and C in Blochs law are evaluated from the data. One finds a smaller value of B in sputtered foils in comparison to the liquid quenched ribbons. There are indications that the mean square range of exchange interaction is larger in these foils.