I.A. Tsoukalas

Magnetic properties of FeMnAl alloys

Abstract The magnetical properties of Fe89−xMn11Alx alloys have been studied by Mossbauer spectroscopy and magnetization measurements. The presented examples show both ferromagnetic (x = 14) and re-entrant ferromagnetic (x = 40) behaviour.

Study of the crystallization of amorphous Fe78Si9B13 and Fe76Si8B16 by means of magnetic measurements

Abstract Measurements of the saturation magnetization of amorphous Fe 78 Si 9 B 13 and Fe 76 Si 8 B 16 as a function of temperature and also as a function of the duration of heating the materials at selected temperatures were made. The results suggest that the crystallization of Fe 78 Si 9 B 13 takes place in two stages, whereas the one of Fe 76 Si 8 B 16 in three. Since, during the initial stage of crystallization, regions of b.c.c. Fe(Si) are formed, measurements of the saturation magnetization of the Fe a Si 1− a ( a = 1,0.9 and 0.75) were also carried out, in order to render possible the calculation of the activation energy of the initial crystallization.

On the influence of Al on the magnetic ground state of 3d ferromagnetic alloys

Abstract This paper describes variations in the mean atomic magnetic moment with Al admixtures in transition element alloys, as functions of the number of 3d + 4s electrons and of the atomic concentration of Al. From the experimental results presented, it seems that the presence of the admixtures results in the completion of the 3d zone of the transition elements. The population increase of the 3d band is interpreted as a consequence of its narrowing and its displacement in the energy spectrum.

Crystallization of amorphous Fe75 − xCuxSi9B16

Abstract In this work the influence of Cu admixtures on the crystallization process of amorphous FeSiB alloys is studied, based on measurements of the saturation magnetization of the series Fe75 − xCuxSi9B16 (x = 0, 1, 2, 2.8 and 3.5) during their heating in selected temperatures. The main conclusion is that the presence of the Cu admixtures accelerates the crystallization, due to the microsegregation that it induces in the alloys.

On the anomalous electrical resistivity in some Ni3[FecAl1-c] alloys

Abstract The electrical resistivity temperature dependence of several Ni3[FecAl1-c] is examined. The negative resistivity coefficient appearing at elevated temperatures is discussed by means of the experimental findings of L12 superstructure formation and the qualitative assumption that the phenomenon is attributed to the order-disorder transformation.

Influence of Cu admixtures on the crystallization of amorphous Fe75Si9B16

Abstract The crystallization of the amorphous alloys Fe 75−x Cu x Si 9 B 16 (x ≤ 4) is completed in three stages: (a) dendritic growth of bcc Fe[Si,Cu], (b) eutectic crystallization of bcc Fe[Si,Cu] + bct Fe 3 B and, finally, (c) formation of bct Fe 3 B. The metastable compound Fe 3 B formed during the second and third stages is eventually dissolved into bcc Fe and bct Fe 2 B. As Cu atoms replace Fe atoms, the kinetics of the whole process is modified because of microsegregation: the first stage is decelerated, the second is accelerated, and the third is accelerated up to 2 at% Cu, but is decelerated at higher concentrations.

Magnetic properties of Ni3FecAl1−c

Abstract The temperature dependence of the magnetization for the Ni3FecAl1-c alloy series is experimentally determined. This magnetic behaviour is simulated by means of a Monte Carlo algorithm using a 1 2 Ising type Hamiltonian taking into account the structure of the alloys. The simulation was made in both homogeneous and in homogeneous distributions of 131 072 atoms in the crystal lattice and proved adequate to explain the magnetic properties of the alloys.

On the electrical properties and α⇆γ transformation of some FeCoNi ternary alloys

Abstract The structural α⇆γ transformation and the electrical resistivity of a series of FeCoNi alloys, of the pseudobinary type (Fe x Ni 1−x ) y Co 100−y were studied as a function of temperature, composition and heat treatment. The temperature range of the measurements was from room temperature up to the Curie point of each alloy. The starting temperature of the γ→α transformation wherever existing was calculated and diagrams showing the magnetic and the structural state of the samples as a function of concentration and temperature, during the temperature decrease, were drawn. The results of the measurements indicate a probable existence of an ordered phase in some of the alloys studied.

Structural investigations of NdFe12-x-yTixNby alloys

Abstract A series of NdFe 12− x − y Ti x Nb y (0.6⩽ x + y ⩽1.1) alloys was prepared by arc melting followed by annealing at temperatures 950°C, 1050°C and 1150°C and water quenching. X-ray diffraction and magnetization measurements showed crystalline phases of ThMn 12 (1:12), Th 2 Zn 17 (2:17) and Nd 3 (Fe,Ti) 29 (3:29) structure types, as well as BCC-Fe and Fe 2 (Ti,Nb) crystalline phases. The volume fraction of the intermetallic compounds rises with the increasing of the annealing temperature. The 1:12 structure type is formed in alloys with p Nb = y /( x + y ) p Nb p Nb >0.5) the 2:17 structure type is observed.

Influence of Al admixtures on the crystal structure and the magnetic properties of 3d transition metal alloys

Abstract We present experimental results from a study of the Md 1−c Al c (c = 0.05, 0.10, 0.15, 0.20) alloy series, where Md represents Fe–Co and Fe–Ni alloys. The results show that the presence of Al atoms in the lattice of the transition alloys causes an expansion of the cell, favors the formation of bimetallic compounds, and diminishes the mean atomic magnetic moment of the transition atoms.