Magnetic measurements and band structure calculations were performed on RT2 and RT5 compounds, where R is a heavy rare-earth and T = Fe, Co, Ni, Al, as well as on pseudobinary compounds GdCo2 − xAx (A = Ni, Cu, Si), YFe2 − xVx and YCo4 − xNixB. The calculated moments per formula unit described well the experimentally determined magnetizations. By considering the 4f–5d–3d exchange interactions, we evaluate the contributions of local 4f–5d and short range 5d–3d interactions to R 5d and Y 4d band polarizations. The 4f–5d induced polarizations are proportional to the De Gennes factor and are the same for a given R and a similar type structure. The R 5d and Y 4d band polarizations induced by R 5d–T3d or Y 4d–T3d hybridizations are proportional to the number of neighbouring T atoms, to a given R, and their magnetic moments. Previous results on the matter are also discussed.

https://iopscience.iop.org/article/10.1088/0953-8984/23/2/026001/pdf

On the R 5d band polarization in rare-earth-transition metal compounds.

The nature of multiple magnetostructural transformations in HoCo2 has been studied by employing magnetic and specific heat measurements, temperature and magnetic field dependent X-ray powder diffraction, and first-principles calculations. Unexpected increase of magnetization observed below the spin-reorientation temperature (TSR) suggests that the low-temperature transition involves a reduction of Co moment. First principles calculations confirm that the paramagnetic cubic to ferrimagnetic tetragonal transformation at TC is assisted by itinerant electron metamagnetism, and that the reduction of Co moment in HoCo2 occurs in parallel with the ferrimagnetic tetragonal to the nearly ferromagnetic orthorhombic transformation at TSRvia the rearrangement of both 3d states of Co and 5d states of Ho. The ac magnetic susceptibility measurements show significant magnetic frustration below TC. In contrast to earlier reports neither ac nor dc magnetic susceptibilities show anomalies in the paramagnetic region obeying the Curie–Weiss law.

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Balancing structural distortions via competing 4f and itinerant interactions: a case of polymorphism in magnetocaloric HoCo2

Magnetic properties of TbCo2 compound at high pressures

Magnetic properties, electronic structures and pressure effects of HoxY1−xCo2 compounds

The presence of a distribution of transition temperatures (DTT) is ubiquitous in materials science. It is common to ascribe deviations from theoretical pure-phase behavior to this fact. To adapt the different pure phase models to systems with a DTT, the parameters of such distribution must be known or at least estimated. In this review, the different sources for the existence of such distributions and their effects on magnetothermal properties are summarized. In addition, different models proposed to extract the parameters of the corresponding DTT are discussed and extended, starting from Weiss model, to account for other phenomenologies. Experimental results on amorphous Fe-Nb-B and intermetallic MnCo(Fe)Ge systems are also reported.

https://digital.csic.es/bitstream/10261/201624/1/metals-10-00226.pdf

Distribution of Transition Temperatures in Magnetic Transformations: Sources, Effects and Procedures to Extract Information from Experimental Data

We have studied electrical resistivity anomalies connected with magnetism in RECo2 (RE=Nd, Tb, Er, Ho) compounds in pressures up to 8 GPa. At ambient pressure the former two compounds exhibit a second order magnetic phase transition (SOMPT) at TC, whereas a first order magnetic phase transition (FOMPT) is observed in the latter two. Although TC decreases with pressure in all four compounds, the TC(P) dependence for NdCo2 and TbCo2 differs considerably from this for HoCo2 and ErCo2. For the latter two, Tc vs P data deviate dramatically from the initial linear dependence above a critical pressure Pc to become almost pressure independent at higher pressures. We propose that this is reflecting the loss of Co metamagnetism that is also indicated by the vanishing resistivity drop at Tc for P>4 GPa and by the change from a FOMPT to a SOMPT. A scenario is discussed assuming that for P>Pc the projected Co 3d density of states at EF decreases. Hence the Co moment collapses because the RE-Co-RE exchange channel beco...

R. Hauser

Papers

Magnetism in rare earth Co2 compounds under high pressures