Probing a ferromagnetic critical regime using nonlinear susceptibility

Abstract

The second order para−ferromagnetic phase transition in a series of amorphous alloys (F e5Co50N i17−xCrxB16Si12) is investigated using nonlinear susceptibility. A simple molecular field treatment for the critical region shows that the third order suceptibility (χ3) diverges on both sides of the transition temperature, and changes sign at T C . This critical behaviour is observed experimentally in this series of amorphous ferromagnets, and the related assymptotic critical exponents are calculated. It is shown that using the proper scaling equations, all the exponents necessary for a complete characterization of the phase transition can be determined using linear and nonlinear susceptiblity measurements alone. Using meticulous nonlinear susceptibility measurements, it is shown that at times χ3 can be more sensitive than the linear susceptibility (χ1) in unravelling the magnetism of ferromagnetic spin systems. A new technique for accurately determining T C is discussed, which makes use of the functional form of χ3 in the critical region.

Amorphous ferromagnetism and re-entrant magnetic glassiness in single-crystallineSm2Mo2O7

“…1 are analyzed according to the Kouvel-Fisher formalism. [87][88][89][90][91][92] This framework allows to obtain a precise estimate of the critical temperature T M C for the transition of the Mo 4+ sublattice, the superscript M referring to the dc magnetometry technique (see the inset of Fig. 3).…”

“…[87][88][89][90][91][92] Here, the slope is determined by the critical exponent γ characteristic of the transition, while the relation T * (T M C ) = 0 holds. The expected linear trend is observed in our data for Sm 2 Mo 2 O 7 (see the inset of Fig.…”

“…9). 89 Within these conditions, the investigated magnetic system can be unambiguously characterized as glassy. 89,118,119,121 Indeed, the divergence of the nonlinear susceptibility was employed as a definitive proof of glassy magnetism also in the case of Y 2 Mo 2 O 7 .…”

Magnetic states and spin-glass properties inBi0.67Ca0.33MnO3: Macroscopic ac measurements and neutron scattering

“…In particular, the spin-glass transition can be robustly characterized by a divergence of the cubic component of the magnetization, which occurs at the temperature of spin-glass order [6]. χ nl measurements has been less used for proving ferromagnetic or antiferromagnetic transitions [7], but allows to evidence an incipient magnetic order (Note that this technique is more usually employed for proving a paraelectic to ferroelectric transition, when analyzing the high order harmonics of the electric susceptibility). A particular interest can be found in the case of multicomponent magnetism where, with the linear susceptibility only, it is often difficult to prove a phase coexistence.…”

Changeover from glassy ferromagnetism of the orbital domain state to long-range ferromagnetic ordering inLa0.9Sr0.1MnO3

“…Studies of the critical regimes in La 0.875 Sr 0.125 MnO 3 revealed that the paramagnetic to ferromagnetic phase transition is accompanied by consistent critical exponents belonging to 3D Heisenberg universility class. 22 However, the low temperature transition which received considerable attention in the last decade remains undetermined. The nature of this low temperature phase previously has been interpreted in terms of canted antiferromagnetic phase 1 .…”