Percolation processes and spin-reorientation ofPrNi5−xCox

Abstract

In the present work we report on the structural and magnetic behaviors of the PrNi 5−x Co x intermetallic compounds. Due to the competition between the anisotropy energies of both Co and Pr sublattices, this series has a spin-reorientation phenomenon at low temperature ͑140 K͒. The Curie temperature, as a function of Co content, has a sudden increase above a critical concentration x c ϳ 1.9 and this feature is assigned as a percolation of geometrically spaced Co clusters. This assumption is explained based on the critical exponent of percolation theory. The series presents therefore a rich magnetic phase diagram, which could be established over a full doping range, i.e., from x =0 to x = 5. We have also studied these compounds on the magnetocaloric point of view and found a quite large full width at half maximum ͑␦T FWHM ͒ of the magnetic entropy change curves for some of the compositions, due to the merging of the ⌬S peaks associated with the spin-reorientation process and the Curie temperature T C . In addition, the series has an appreciable relative cooling power, which is therefore suitable to be used in a magnetic refrigerator operating in a large range of temperature.

The study of the magnetic and room-temperature magnetocaloric properties in spin-reorientation Nd1−xDyxCo4Al (x=0, 0.1) alloys

“…Therefore, MCE resulted from materials possessing the SR transition could be expected [12][13][14][15]. Until now, the MCE in SR materials is mostly obtained at relatively low temperature [12][13][14][15]. As a result, the investigation of room-temperature MCE in SR materials is of importance.…”

“…It is well known that the spin-reorientation (SR) transition manifests itself by a rotation of the easy magnetization direction and is often accompanied by an abrupt change of the magnetization [9][10][11]. Therefore, MCE resulted from materials possessing the SR transition could be expected [12][13][14][15]. Until now, the MCE in SR materials is mostly obtained at relatively low temperature [12][13][14][15].…”

“…NdCo 5 is a ferromagnetic intermetallic compound crystallizing in a hexagonal CaCu 5 -type structure with P6/mmm space group [16][17][18][19]. In this compound, the magnetocrystalline anisotropy (MCA) of Co sublattice favors the c axis (first-order anisotropic constant K 1Co > 0), while the Nd sublattice tends to have a planar (a-b plane) MCA (K 1Nd < 0) because of a negative value for the secondorder Stevens factor˛J [15]. With the increasing temperature, it undergoes two SR transition [9].…”

Ab Initio Investigation of the Spin-Reorientation Phase Transition in PrCo₅₋ₓNiₓ (x = 0-5)

“…When the temperature rises, in PrCo 3 Ni 2 magnetic moment becomes directed along the c axis [6]. This combination of very high ordering temperatures and large magnetostriction in this system makes it promising for magnetic refrigerator applications [7].…”

Copper-doping effects in electronic structure and spectral properties of SmNi5

“…The RNi 5 group of intermetallic compounds (where R is a rare earth) and their substitutional derivatives have been extensively studied because of a variety of interesting properties promising for practical applications, such as magnetocaloric effect, hydrogen storage capacity, magnetic anisotropy and high coercivity [1][2][3][4][5][6]. Their diverse magnetic and electronic characteristics are associated with both localized moments of R atoms and itinerant electrons of Ni atoms in hexagonal CaCu 5 -type structure.…”