Itinerant-electron metamagnetism and the onset of ferromagnetism in Laves phase compounds

Abstract

Detailed magnetization measurements have been carried out for Laves phase compounds which have a C15-type structure up to x = 0.220. A clear increase in the lattice constant occurs at room temperature in the vicinity of x = 0.095, corresponding to the critical concentration of the onset of ferromagnetism. A representative first-order metamagnetic transition was observed in the compounds with x = 0.090 and 0.093 in relatively low fields below 9 T. The critical temperature from the first- to second-order metamagnetic transition in both compounds and the susceptibility maximum temperature for several paramagnetic compounds were obtained. It should be noted that practically coincides with for x = 0.093, very close to the critical concentration of the onset of ferromagnetism. This result is well explained by the recent theory associated with spin fluctuations. The temperature shifts to lower temperatures with increasing x and disappears at x = 0.095 and above, correlated with the onset of ferromagnetism also. The spontaneous magnetization per Co atom exhibits a maximum value of at x = 0.110, whereas the Curie temperature does not show a maximum value at the same composition.

Itinerant-electron metamagnetism and susceptibility maximum behavior in several kinds of Laves-phase compounds

“…In addition, Y(Co 1−x Al x ) 2 [19], Lu(Co 1−x Al x ) 2 [15,20] and Lu(Co 1−x Ga x ) 2 [12,15] into consideration [18] has been verified experimentally in well-homogenized Lu(Co 1−x Al x ) 2 and Lu(Co 1−x Ga x ) 2 compound systems [21].…”

“…In connection with such a shape of the DOS in these compounds, a broad maximum in the temperature dependence of magnetic susceptibility χ i.e. χ maximum behavior is observed [12,15,17]. Such a finite temperature behavior has been explained by the free energy renormalized by spin fluctuations [16,18].…”

“…The critical field of the itinerant-electron metamagnetic transition of YCo 2 and LuCo 2 has been reported to be 69 and 74 T, respectively [2,3]. The corresponding quasi-binary systems have a relatively low critical magnetic field µ 0 H c for the itinerant-electron metamagnetic transition [4][5][6][7][8][9][10][11][12][13][14][15]. The itinerant-electron metamagnetic transition is closely associated with the shape of the density of states (DOS) which is characterized by a sharp peak just below the Fermi energy E F [16].…”

Concentration Dependence of Pressure Effect in La(Fe<I><SUB>x</SUB></I>Si<SUB>1&minus;<I>x</I></SUB>)<SUB>13</SUB> Compounds

“…[1][2][3][4][5] We have demonstrated that La(Fe x Si 1Àx ) 13 compounds with 0:86 x 0:90 exhibit a first-order magnetic phase transition at the Curie temperature T C , and also the IEM transition above T C . [6][7][8] Furthermore, large magnetovolume effects such as a large pressure coefficient of T C are followed by the IEM transition.…”

Thermal Expansion Characteristics Associated with Spin Fluctuations under Applied Magnetic Field and High Pressure for Lu(Co0.9Ga0.1)2Laves-Phase Compound

“…1,2) By making pseudo-binary Lu(Co 1 x Ga x ) 2 Laves-phase compounds (0.00 x 0.09), the critical transition field is decreased. 3,4) In the compound with x = 0.10, the ferromagnetic state appears below 40 K. 3,4) Since Lu(Co 0.90 Ga 0.10 ) 2 compound is on the boundary concentration of the onset of ferromagnetic phase, 3) the energies in the ferromagnetic and paramagnetic state are very close each other. Therefore, the magnetovolume coupling energy plays an important role in the phase transition.…”