Kinetic arrest of the first-order $R\bar {3}c$ toPbnmphase transition in supercooled La_xMnO_3+δ(x= 1 and 0.9)

Abstract

We report the occurrence of kinetic arrest of the first-order phase transition from R3c to Pbnm in supercooled La(x)MnO(3±δ) (x = 1 and 0.9, i.e. δ > 0.125). Structural studies have been done, employing low temperature transmission electron microscopy (LT-TEM) and low temperature x-ray diffraction (LT-XRD) techniques. No phase transformation was observed even in La(x)MnO(3±δ) aged for ~12 h at 98 K. The evidence of the occurrence of kinetic arrest was realized at low temperatures through in situ electron beam triggered nucleation and perpetual devitrification of the R3c phase into a Pbnm phase. It was clearly evidenced that the R3c structure of La(x)MnO(3±δ), below its ferromagnetic transition temperature, is metastable and prone to be transformed to a Pbnm orthorhombic structure following initiation by an electron beam trigger. The electron beam transformed Pbnm phase was found to transform back to the R3c phase through a first-order phase transition occurring close to the ferromagnetic to paramagnetic transition (T(c)) during heating. The glass-like kinetics of the arrested R3c phase has been investigated through resistance relaxation measurements, showing a decreasing logarithmic rate of decay of the arrested R3c phase towards the stable Pbnm phase with decreasing temperature, down to 5 K. On the basis of the correlations observed in the resistance-versus-temperature, magnetization-versus-temperature, magnetization-versus-field, resistance relaxation and LT-XRD measurements, the occurrence of kinetic arrest has been attributed to the suppression of Jahn-Teller distortion by double exchange across the insulator-metal transition.

Elusive Valence Transition in Mixed-Valence Sesquioxide Cs4O6

“…If cooling is allowed to occur slowly, charge localization is accompanied by charge ordering that induces a structural phase transition. Similar out-of-equilibrium kinetic arrest phenomena upon charge ordering have been previously studied in several rare-earth manganites. − In the valence-localized and charge-ordered tetragonal phase, the reduced symmetry allows two distinct O–O sites in a 1:2 ratio with significantly different bond lengths that confirm the presence of superoxide and peroxide groups. The material can therefore be described by the formula (Cs + ) 4 (O 2 – ) 2 (O 2 2– ) and classified as a Robin–Day Class II mixed-valence system.…”

Kinetic-arrest-induced phase coexistence and metastability in(Mn,Fe)2(P,Si)

“…A similar phenomenon has been reported in diverse classes of magnetic systems, such as Gd 5 Ge 4 [16], Ni-Mn-X based Heusler alloys [17][18][19], doped-FeRh [20], Nd 7 Rh 13 [21], Tb 4 LuSi 3 [22], and manganites [23][24][25][26][27]. The kinetically arrested phase transition is associated with a strong magne-* x.f.miao@tudelft.nl tostructural coupling in these magnetic systems.…”

Effect of oxygen off-stoichiometry on coupled structural and magnetic phase-transitions in La0.15Sr0.85MnO3−δ (δ=0.02, 0.14)

“…For example, fatigue in the switching of ferroelectric non-volatile RAM devices [15], degradation of the dielectric and piezoelectric properties [16], induction of ferromagnetism and metal-insulator transition [17], affecting the spin and charge ordered states [18] and the memory effect [19]. Such effects of oxygen off-stoichiometry on the structural, magnetic and electrical properties of LaMnO 3-δ [20][21][22] , A-site deficient La 1-x MnO 3±δ [22][23][24] and hole doped La 1-x [27,28] and oxygen non-stoichiometry are available [29][30][31]. In this article we report the effect of oxygen off-stoichiometry on the behavior of coupled structural and magnetic phase-transitions in La 0.…”