The magnetic characteristics of chromium and iron containing MnNiGe-based alloys with several types of quenching and annealing were investigated. It was found that the quenched Mn0.89Cr0.11NiGe has a ...spontaneous and magnetic field induced magnetostructural first-order transitions at room temperature. These transitions might be accompanied by a large magnetocaloric effect. In general, Mn0.89Cr0.11NiGe can be classified as promising material for use in the magnetocaloric application at room temperatures. The first order magnetostructural phase transition from the ferromagnetic to paramagnetic state is not realized in MnNi0.90Fe0.10Ge. In contrast to Mn0.89Cr0.11NiGe, however, the FM state in quenched-on-wheel MnNi0.90Fe0.10Ge is preserved to the lowest temperatures. Based on the set of the magnetic properties, it has been concluded that the iron containing MnNiGe-based alloys are less promising for practical use.
The magnetic and structural characteristics of the solid solutions MnNi.sub.1-xFe.sub.xGe (0.10 ≤ x less than or equal to 0.25) have been investigated. At T = 290 K, the solid solutions have a ...hexagonal structure of the Ni.sub.2In type. The magnetic properties of MnNi.sub.1-xFe.sub.xGe (0.10 ≤ x less than or equal to 0.25) weakly depend on the type of heat treatment. Based on the magnetometric and Mossbauer data, it has been found that, in the solid solutions MnNi.sub.1-xFe.sub.xGe (0.10 ≤ x less than or equal to 0.25) with iron concentrations x = 0.10-0.15, the iron atoms are statistically distributed over the octahedral and trigonal-bipyramidal positions. At concentrations above xx = 0.15, iron atoms replace only the manganese atoms in the octahedral positions, whereas nickel atoms in the trigonal-bipyramidal positions are not replaced by the iron atoms. DOI: 10.1134/S1063783415120094
The analysis of 57Fe Mossbauer spectroscopy results for cation and anion substituted Mn sub(2-x)Fe sub(x)P sub(1 -y)As sub(y) was done in order to find out the influence of the Mn/Fe ratio on the ...magnetic properties of solid solutions and to compare experimental hyperfine parameters with those calculated from firstprinciples. The correlation between third Mossbauer sextet in Mn sub(2-x)Fe sub(x)P sub(0 .5)As sub(0.5) spectrum at 77K and stabilization of the antiferromagnetic phase for x = 0.5-0.6 was found on the basis of comparison between the magnetic phase diagrams and the "hyperfine field - iron content" dependence. The observed qualitative difference for Mn sub(2-x)FexP sub(0.5)As sub(0.5) and MnFeAs sub(y)P sub(1-y) "hyperfine field - concentration" diagrams was interpreted on the basis of different mechanisms of magnetic phase stabilization and the different configurations of tetrahedral anionic environment of iron ions for systems with cation and anion substitutions.
The structure, hyperfine interactions and magnetic properties of the series of multiferroic Bim+1Ti3Fema3O3m+3 Aurivillius compounds with m=4a8 were studied using X-ray diffraction, 57Fe Mossbauer ...spectroscopy and vibrating sample magnetometry. Samples were prepared by the conventional solid-state sintering method. Bulk magnetic measurements showed that for m=4 the compound is paramagnetic down to 2 K while in the compound with m=5 the antiferromagnetic type transition was observed at 11 K. In the case of compounds with m=6a8 much more complex magnetic behavior was found. For these compounds a gradual spin freezing and antiferromagnetic spin glass-like ordering were observed on decreasing temperature. The temperature of spin glass freezing was determined as 260, 280 and 350 K for m=6, 7 and 8, respectively. Room-temperature Mossbauer spectra of all the compounds studied confirm their paramagnetic state. However, liquid nitrogen and liquid helium temperature measurements reveal magnetic ordering with a residual paramagnetic phase contribution for the compounds with m=5a8.
The structure, hyperfine interactions and magnetic properties of the series of multiferroic Bi(m+1)Ti(3)Fe(m-3)O(3m+3) Aurivillius compounds with m=4-8 were studied using X-ray diffraction, (57)Fe ...Mossbauer spectroscopy and vibrating sample magnetometry. Samples were prepared by the conventional solid-state sintering method. Bulk magnetic measurements showed that for m=4 the compound is paramagnetic down to 2 K while in the compound with m = 5 the antiferromagnetic type transition was observed at 11 K. In the case of compounds with m = 6-8 much more complex magnetic behavior was found. For these compounds a gradual spin freezing and antiferromagnetic spin glass-like ordering were observed on decreasing temperature. The temperature of spin glass freezing was determined as 260, 280 and 350 K for m = 6, 7 and 8, respectively. Room-temperature Mossbauer spectra of all the compounds studied confirm their paramagnetic state. However, liquid nitrogen and liquid helium temperature measurements reveal magnetic ordering with a residual paramagnetic phase contribution for the compounds with m = 5-8.
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