First-order nature of the ferromagnetism in CeIn2investigated using muon spin rotation and by systematic substitution of La for Ce

Abstract

The nature of the first-order ferromagnetic transition in binary CeIn 2 alloy is investigated by muon spin rotation (μSR) measurements and chemical substitution of Ce by La in the La 1−x Ce x In 2 (0.9 x 1.0) series of alloys. Below 22 K, the analysis of μSR spectra shows two spin precession frequencies associated with the local field at the muon site created by the surrounding ferromagnetic ordered magnetic moments. These frequencies abruptly disappear above T C , indicating the first-order character of this transition, as previously reported. For temperatures between 22 and 24 K, the shape of the μSR spectra indicates the existence of an additional magnetic phase with features of an incommensurate magnetic structure. The presence of this magnetic phase is supported by dc(ac)-magnetic susceptibility and specific-heat results obtained on chemical diluted samples, which also show a magnetic contribution above the ferromagnetic transition. The combined analysis of these results clarifies the first-order character of the ferromagnetic transition in CeIn 2 , based on the existence of an intermediate magnetic phase between the paramagnetic and ferromagnetic states.

Metallic quantum ferromagnets

“…This conclusion on the basis of discontinuities at T C in the resistivity, the thermal expansion, and the magnetic entropy was later corroborated by µSR measurements (Rojas et al, 2011). Application of hydrostatic pressure increases T C (Mukherjee et al, 2012), but upon doping with lanthanum T C decreases, to about 19.4 K in La 1−x Ce x In 2 with x = 0.9, and the transition remains first order (Rojas et al, 2011). The same µSR measurements indicated the existence of a second magnetic phase with long-range order in between the FM and PM phases.…”

“…Lanthanide-based compounds a. La1−xCexIn2 CeIn 2 crystallizes in the orthorhombic CeCu 2 structure and undergoes a first-order transition to a FM state at T C = 22 K (Rojas et al, 2009). This conclusion on the basis of discontinuities at T C in the resistivity, the thermal expansion, and the magnetic entropy was later corroborated by µSR measurements (Rojas et al, 2011). Application of hydrostatic pressure increases T C (Mukherjee et al, 2012), but upon doping with lanthanum T C decreases, to about 19.4 K in La 1−x Ce x In 2 with x = 0.9, and the transition remains first order (Rojas et al, 2011).…”

Itinerant ferromagnetism with finite-ranged interactions

“…Metallic systems in the vicinity of second order phase transitions display remarkable quantum critical phenomena. 1 However, in several metals 2 quantum criticality gives way to a first order transition, [3][4][5][6][7] or spatially modulated magnetic order, [8][9][10] or a p-wave superconducting instability. [11][12][13][14][15] A generic phase diagram for many metallic ferromagnets has emerged containing a first order magnetic transition with nearby instabilities into exotic phases.…”

Substitutional effects of In by Cu in CeIn2

“…not affect the stability of the crystallographic orthorhombic structure, which remains the same in all the substituted samples [5]. However, in the Ce(In 1−x Cu x ) 2 series, the crystallographic structure changes from orthorhombic (Imma for x = 0) to hexagonal P6/mmm for the Cu-diluted sample with x = 0.05.…”

“…In this context, the nature of the first-order ferromagnetic (FM) transition (T C = 22 K) of the CeIn 2 alloy [4] has been studied by combining chemical substitution with muon spin rotation spectroscopy (μSR) experiments, which unveiled the existence of an intermediate antiferromagnetic phase around 23 K [5].…”