Relating supercooling and glass-like arrest of kinetics for phase separated systems: DopedCeFe2and(La,

Kranti Kumar

¹

,

A. K. Pramanik

²

,

A. Banerjee

³

et al.

Abstract

Coexisting ferromagnetic and antiferromagnetic phases over a range of temperature as well as magnetic field have been reported in many materials of current interest, showing disorder-broadened 1st order transitions. Anomalous history effects observed in magnetization and resistivity are being explained invoking the concepts of kinetic arrest akin to glass transitions. From magnetization measurements traversing novel paths in field-temperature space, we obtain the intriguing result that the regions of the sample which can be supercooled to lower temperatures undergo kineticarrest at higher temperatures, and vice versa. Our results are for two diverse systems viz. the inter-metallic doped CeFe2 which has an antiferromagnetic ground state, and the oxide La-Pr-Ca-Mn-O which has a ferromagnetic ground state, indicating the possible universality of this effect of disorder on the widely encountered phenomenon of glass-like arrest of kinetics.

Magnetism in gallium-dopedCeFe2: Martensitic scenario

“…[14][15][16][17][18][19][20] Among the intermetallics, Gd 5 Ge 4 is known to show many similarities with the oxides. 11,23 Though there are several factors thought to be responsible for the multistep behavior, the most striking and accepted reason common to the oxide materials and the intermetallics seems to be the martensitic transition driven by the applied field. It has been proposed that the temperature 33 and the magnetic-field-induced 12 phase evolution in these systems resemble that of a martensite.…”

“…A few attempts have also been reported wherein the similarities between the intermetallic and oxide scenarios are compared to establish the universality of the phenomena responsible for the step behavior. 11,23 Results on the Ru-and Re-doped CeFe 2 alloys show that they also possess a phase-separated magnetic structure while varying the field and ͑or͒ temperature. 9 In fact, among the substituted CeFe 2 compounds, until date, Ru and Re are the only two substituents that are known to result in sharp magnetization step behavior.…”

Conversion of a glassy antiferromagnetic-insulating phase to an equilibrium ferromagnetic-metallic phase by devitrification and recrystallization in Al substituted Pr0.5Ca0.5MnO3

“…regions with above-average T* have below-average T K . It is rather intriguing, that such anti-correlation was shown to be universal for all other systems where the 'magnetic glassy' states are identified 10,14,15 . Evidence of the anticorrelation is clear in Fig.…”

“…3(c) of Ref. 10 ). We stress that the CHUF measurements not only allows to identify both the existence and magnetic order of the 'magnetic glassy' state but goes deeper to probe correlation between T* and T K without taking recourse to time domain 16 .…”

“…Our measurements of magnetization as a function of temperatue show topologically different features depending on the sign of (H h -H c ). We shall link this with our proposed phenomenology 9,10 . We have recently reported that while the arrested glass-like FM-M state in LCMO devitrifies on heating, cooling after annealing causes better recrystallization to AF-I state 8 .…”