Anna Bajorek

Magneto-History Effect in the Tb_{x}Gd_{1-x}Ni_3 Compounds

The compounds TbxGd1−xNi3 with a PuNi3-type structure have been obtained. The magnetic properties have been investigated by using SQUID magnetometer (Quantum Design MPMS, temperature from 1.9 K to 300 K and magnetic eld up to 7 T). The partial replacement of Gd by Tb atoms is re ected in a decrease of the ordering temperature from 115 K (x = 0.0) to 81 K (x = 1.0) as well as the increase of the saturation magnetic moment MS from 6.93 μB/f.u. (x = 0.0) to 7.14 μB/f.u. (x = 1.0). A large di erence of M(T ) curves has been noticed between the so-called eld cooling zero eld cooling magnetization. The thermomagnetic curves are sensitive to the applied magnetic eld and their origin can be understood as the domain-wall pinning e ect and as the temperature dependence of coercivity.

Magnetic Properties of the Gd1-xTbxNi3 Intermetallic Compounds

The paper presents selected magnetic properties of the Gd1-xTbxNi3 intermetallic compounds. Based on the wide-ranging SQUID magnetometer (Quantum Design MPMS, temperature from 1.9K to 300K and magnetic field up to 7T) series of different magnetic measurements were carried out. In studied system the saturation magnetization and the Curie temperature strongly depends of Tb concentration. Moreover, the so-called field cooling - zero field cooling (FC-ZFC) curves reveal a dependence of M(T) on the applied magnetic field. The thermomagnetic curves indicate interesting behaviour which is typical for terbium compounds and can be ascribed to the interaction between different aligned magnetic subblattices.

Unusual magnetic properties of YbxGdl-xNi5 (x?0.5) intermetallics

In the presented paper we are focused on the magnetic properties of the hexagonal YbxGd1-xNi5 intermetallic compounds. Based on wide-ranging SQUID magnetometer (Quantum Design MPMS, temperature from 1.9K to 400K and magnetic field up to 7T) series of different magnetic measurements were carried out. It was shown that saturation magnetization and the Curie temperature strongly depends of Yb concentration. Moreover, the so-called field cooling – zero field cooling (FC-ZFC) curves reveal an unexpected existence of negative magnetization M in a certain temperature range. The possible origin of the diamagnetic behaviour, observed in doped samples, has been rather ascribed to the interaction between more than one opposite aligned magnetic sublattices.

The Nanoflower-Like Morphology and Magnetism of As-Milled Ho(Ni0.8Co0.2)3 Powders Prepared by HEBM

The morphology and magnetic properties of the Ho(Ni0.8Co0.2)3 crystalline and ball – milled intermetallic compounds are presented. The polycrystalline bulk compound crystallizes in the rhombohedral PuNi3 - type of crystal structure and indicates ferrimagnetic arrangement with the Curie temperature of TC = 48 ± 1 K, the helimagnetic temperature Th = 26 ± 2 K with the total saturation magnetic moment of 7.78 µB/f.u. at 2 K. The use of the HEBM method leads to the formation of nanoflakes with typical thickness of less than 100 nm. The extended milling leads to the reduction in particles/crystallites size and in the emergence of the relatively small coercivity (HC).

Microstructure and electrical resistivity in the GdNi 5− x Cu x intermetallic series

Abstract The effect of the Ni/Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi5–xCux series was studied. The value of temperature of phase transition (Tph) estimated from temperature dependence of electrical resistance varied non-linearly across copper doping from 32.5 K (x=0.0) to 29.1 K (x=5.0). The value of residual resistivity (ρo) estimated at low temperature range decreased from 27.28 μΩcm (x=0.0) to 9.44 μΩcm (x=5.0), which was discussed as the influence of microstructure. In order to describe the temperature dependence of resistivity ρ(T) a variety of approaches were applied due to different scattering mechanisms occurring at high and low temperature ranges. The change within ρ(T) curvature was evidenced at low temperature range across copper doping. The temperature variation of the resistivity was quite peculiar for Cu-rich compounds (x=4.8, x=5.0), which might be correlated with the incommensurate magnetic structure derived from the weakly negative interaction between the nearest neighbours of Gd. The correlation between microstructure and resistivity was observed.

Effect of In/Sn substitution on magnetism, crystal and electronic structure in Gd(In1-xSnx)3 system

The magnetic, electric transport and electronic structure of a series of polycrystalline intermetallic compounds were investigated by means of experimental and ab initio methods. For all investigated compounds, the multiple magnetic phase transition was detected by means of magnetization and resistivity measurements. Partial replacement of In by Sn atoms is reflected in the oscillating behaviour of the upper Néel temperature () and other magnetic parameters but the lower Néel temperature () remains almost constant. Electronic structure studied by method indicates that the In/Sn substitution results in an energy shift of the Gd4f and Gd4d lines and a reconstruction of the valence band (VB) near the Fermi level. Especially, the maximum intensity near the Fermi level varies with Sn content in an oscillatory manner. The observed peculiar features of the electronic structure of the alloys have been reproduced by ab initio density functional calculations. For all compounds, the calculations disclosed the presence of two, close energetically, ground-state antiferromagnetic structures of AFM-I (0 0 1) and AFM-III (1 1 0) type. The ab initio study revealed also that upon the In/Sn substitution, the ground-state magnetic structure of the compounds changes from AFM-III type for the In-rich side to AFM-I type for a higher Sn content. Our experimental and theoretical investigations demonstrated unambiguously that the observed oscillatory variation of different magnetic parameters of the is driven by the changes in the VB structure of the system upon the In/Sn substitution.