Abstract
The nature of the first-order ferromagnetic transition in binary CeIn${}_{2}$ alloy is investigated by muon spin rotation ($\ensuremath{\mu}$SR) measurements and chemical substitution of Ce by La in the La${}_{1\ensuremath{-}x}$Ce${}_{x}$In${}_{2}$ ($0.9\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0$) series of alloys. Below 22 K, the analysis of $\ensuremath{\mu}$SR 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 $\ensuremath{\mu}$SR 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.
Highlights
First-order phase transitions are a relevant topic in condensed-matter physics and materials science from both experimental and theoretical points of view because they are related to interesting phenomena such as colossal magnetoresistance,[1] giant magnetocaloric effects,[2] and memory shape effects.[3]
A typical example is those materials in which ferromagnetic quantum phase transitions display a behavior that can be well explained in terms of a first-order transition
Due to its microscopic character and sensitivity to extremely small internal fields, it can reveal spatially inhomogeneous magnetic features associated with the influence of the crystalline environment on the muon spin motion. We have used this useful tool in the investigation of the nature of the first-order ferromagnetic transition in the CeIn2 alloy
Summary
First-order phase transitions are a relevant topic in condensed-matter physics and materials science from both experimental and theoretical points of view because they are related to interesting phenomena such as colossal magnetoresistance,[1] giant magnetocaloric effects,[2] and memory shape effects.[3] The order of a phase transition is an important issue related to the understanding of quantum phase phenomena.[4,5] A typical example is those materials in which ferromagnetic quantum phase transitions display a behavior that can be well explained in terms of a first-order transition. Several mechanisms have been identified that preempt ferromagnetic quantum criticality by a first-order transition. The effect of quenched disorder on a first-order phase transition has been a subject of considerable scientific interest since the late 1970’s. There are several distinct examples: disordered-ferroelectric transitions,[6] the vortex-matter phases of high-temperature superconductors (HTSs),[7] and electronic phase separation in manganites showing colossal magnetoresistance.[8]
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