Irreversibility of the magnetic state ofTm1−xTbxCo2revealed by specific heat, electrical resistivity, and neutron diffract

Abstract

The substitution of Tb for Tm in the Laves phase compound TmCo 2 leads to appearance of a magnetic moment on the Co atoms through the metamagnetic transition in the itinerant d-electron subsystem and gives rise to long-range ferrimagnetic order in Tm 1−x Tb x Co 2 at x ജ 0.15. The magnetic state of the compound Tm 0.9 Tb 0.1 Co 2 , i.e., just below the critical Tb concentration, is characterized by the presence of large regions with short-range magnetic order and localized spin fluctuations ͑LSFs͒ induced in the Co 3d-electron subsystem by the fluctuating f-d exchange due to the Tm-Tb substitution. The peculiar magnetic state of this compound is strongly influenced by an external magnetic field which produces a first-order magnetic phase transition to a long-range ferrimagnetic state with the magnetic moment on the Co atoms up to ͑0.7-0.8͒ B. This field-induced transition in Tm 0.9 Tb 0.1 Co 2 is found to be irreversible. It is accompanied by a giant and irreversible reduction of the electrical resistivity ͑⌬ / ϳ −45% ͒, specific heat ͑by about 3.7 times at 2 K͒, and intensity of magnetic neutron scattering. Such behavior is associated with the field-induced metamagnetic transition in the itinerant d-electron subsystem mediated by the f-d exchange. Significantly enhanced values of the residual resistivity and the coefficient ␥ of the T-linear contribution to the specific heat in the compound with x = 0.1 as well as their unusual behavior with temperature and under application of the magnetic field is ascribed to the presence of LSF.

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

“…Among magnetic materials, RCo 2 compounds (R = rare earth) having the Laves phase structure of C15 type have attracted particular interest [ 1 , 2 ]. Attention to these materials is mainly due to their attractive properties, which strongly depends on the type of rare-earth element in the composition [ 3 ].…”

Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound

“…In the RCo 2 compounds with magnetic R ions, in the ordered state, the molecular field H mol may exceed the critical field required to induce the metamagnetic Materials 2020, 13, 5481 2 of 14 transition in the d-electron subsystem [5,8]. The molecular field enhanced by the external magnetic field can easily exceed the critical value Hc, resulting in an increase of the magnetic moment of Co up to a value of about 1 µ B [5,8,9]. It is known that RCo 2 compounds show a magnetic structure with parallel or antiparallel alignments of the magnetic moments of R and Co ions, for light or heavy R elements, respectively [8].…”

“…The molecular field enhanced by the external magnetic field can easily exceed the critical value Hc, resulting in an increase of the magnetic moment of Co up to a value of about 1 µ B [5,8,9]. It is known that RCo 2 compounds show a magnetic structure with parallel or antiparallel alignments of the magnetic moments of R and Co ions, for light or heavy R elements, respectively [8]. Substitution of other kinds of atoms with RCo 2 results in a new family of compounds called pseudo-binaries like the R(Co 1−x T x ) 2 , the R 1-y R' y Co 2 or even four-component R 1−y R' y (Co 1−x T x ) 2 compounds.…”

Theoretical study of magneto‐electronic properties of TmCo2 and NdCo2 intermetallic compounds through density functional theory calculations

“…Similarly, they demonstrated results of the complex character of the Tm 1 − x Tb x Co 2 compounds around the critical concentration in the subsystem of 3d states of the Cobalt element (Co). [ 8 ] Furthermore, the lines of the PE resonant spectra of the RT 2 binary compounds (R = Ce, Pr, Nd; T = Co, Rh, Ir) have been studied by Y. Kucherenko et al [ 9 ] within the framework of SIAM. In 2019, J. Šebesta and coworkers [ 10 ] studied experimentally the lattice distortion in TmCo 2 compound using a low‐temperature X‐ray diffraction (XRD).…”