Pressure effects on the magnetic and transport properties ofPr1−xSrxMnO3crystals nea

Abstract

Effects of hydrostatic pressure up to 11 kbar on the magnetic and transport properties of Pr 1−x Sr x MnO 3 ͑PSMO͒ were investigated in single crystals with various doping level: x = 0.22, 0.24, 0.26, in a wide range of temperature. In similarity with other low doped manganites, PSMO exhibits a metal to insulator transition and magnetoresistance maxima at the same temperature T = T MI . It was found that the magnetic ordering temperature T C of the Mn spin sublattice and T MI increase linearly upon applying the pressure. The pressure coefficients dT C / dP and dT MI / dP of PSMO enhance around percolation threshold at x = x C = 0.24 upon increasing the doping level. According to the magnetization measurements it appears that the nature of the ferro-toparamagnetic phase transition in PSMO also varies at the crossover region, in a similar manner to that of La 1−x Ca x MnO 3 . At ambient pressure the transition for x = 0.22 is of a second order while for x = 0.26 it is of a first order, a nature of a transition for x = 0.24 is not well defined yet. The effect of pressure of ϳ11 kbar on the kind of the magnetic phase transition is clearly seen in the case of x = 0.24 sample. Applied pressure changes the character of the phase transition from nearly a continuous one at P = 0 to more abrupt, almost discontinuous one at P = 10.7 kbar. Measurements of magnetization and of ac susceptibility employed in our studies indicate upon an ordering of the Pr magnetic subsystem and a cluster glass behavior at temperatures T C ͑Pr͒ ͑80-100 K͒, much lower than T C ͑165-205 K͒. All of the results obtained are discussed with regards to existing models of magnetic and transport properties of low doped manganites.

Spin-glass-like properties ofLa0.8Ca0.2MnO3nanoparticles ensembles

“…Double exchange is more sensitive to the pressure than SE and therefore the pressure coefficients are significantly different: dT C / dP Ϸ 0.2-0.3 K / kbar and dT C / dP Ϸ 2 K/ kbar for x Ͻ x C and x Ͼ x C , respectively. 55 Since the pressure coefficient dT C / dP Ϸ 1.8-1.9 K / kbar is very close for our NPs ensembles to that of metallic La 1−x Ca x MnO 3 ͑x Ͼ x C ͒ bulk manganites it seems reasonable to assume that a dominant magnetic interaction in the NPs cores is the ferromagnetic DE. For all fine-particle systems, different interparticle interactions exist and play a decisive role in formation of collective states and determine magnetic behavior of NP ensembles.…”

“…55 In the case of x Ͼ x C , FM double exchange ͑DE͒ interactions control the magnetic and transport properties, whereas at x Ͻ x C DE is partly replaced by superexchange ͑SE͒ FM interactions. Double exchange is more sensitive to the pressure than SE and therefore the pressure coefficients are significantly different: dT C / dP Ϸ 0.2-0.3 K / kbar and dT C / dP Ϸ 2 K/ kbar for x Ͻ x C and x Ͼ x C , respectively.…”

Electric field tuning of phase separation in manganite thin films

“…The parameter A = (1 − f c )/f c , with f c being the percolation threshold. The GEM theory has been demonstrated to describe well the transport properties of phase-separated manganites [88][89][90], Although the generally accepted three-dimensional value of f c is 0.16, Kim et al found that f c = 0.17 presents a better fit for La 5/8−x Pr x Ca 3/8 MnO 3 (LPCMO) single crystals, whereas even higher values in the range of 0.22-0.24 were found for manganite thin films [88,89,91]. This discrepancy was attributed to both the quasi-two-dimensional nature of the films and the difference of the assumed values of σ M and σ I from the actual ones [88].…”

AC-susceptibility study of films on and

“…It has been known for decades that measurements of the initial susceptibility yield important information on magnetic domain processes [18,19]. Accordingly, ACsusceptibility has been used as a probe to study magnetic inhomogeneities due to phase separation in manganite single crystals [20][21][22][23] and the influence of preparation conditions on the magnetic properties in manganite ceramics [24]. Moreover, it has been established that ACsusceptibility can be a powerful tool to study magnetic inhomogeneities in manganites films [25].…”