title: Pressure-induced colossal piezoresistance effect and the collapse of the polaronic state in the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn2O7.
abstract: We have investigated the effect of hydrostatic pressure as a function of temperature on the resistivity of a single crystal of the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7). Whereas a strong insulating behaviour is observed at all temperatures at ambient pressure, a clear transition into a metallic-like behaviour is induced when the sample is subjected to a pressure (P) of ~1.0 GPa at T < 70 K. A huge negative piezoresistance ~10(6) in the low temperature region at moderate pressures is observed. When the pressure is increased further (5.5 GPa), the high temperature polaronic state disappears and a metallic behaviour is observed. The insulator to metal transition temperature exponentially increases with pressure and the distinct peak in the resistivity that is observed at 1.0 GPa almost vanishes for P > 7.0 GPa. A modification in the orbital occupation of the e(g) electron between 3d(x(2)-y(2)) and 3d(z(2)-r(2)) states, as proposed earlier, leading to a ferromagnetic double-exchange phenomenon, can qualitatively account for our data.
authors.affiliation: Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620024, India.
authors.forename: R
authors.initials: R
authors.lastname: Thiyagarajan
authors.forename: N
authors.initials: N
authors.lastname: Manivannan
authors.forename: S
authors.initials: S
authors.lastname: Arumugam
authors.forename: S
authors.initials: S
authors.lastname: Esakki Muthu
authors.forename: N R
authors.initials: NR
authors.lastname: Tamilselvan
authors.forename: C
authors.initials: C
authors.lastname: Sekar
authors.forename: H
authors.initials: H
authors.lastname: Yoshino
authors.forename: K
authors.initials: K
authors.lastname: Murata
authors.forename: M O
authors.initials: MO
authors.lastname: Apostu
authors.forename: R
authors.initials: R
authors.lastname: Suryanarayanan
authors.forename: A
authors.initials: A
authors.lastname: Revcolevschi
mesh_terms: D017097:Electric Impedance; D004583:Electrons; D017895:Manganese Compounds / Q000737:chemistry*; D044367:Phase Transition; D011312:Pressure; D011789:Quantum Theory; D013696:Temperature
chemical_list: D017895:Manganese Compounds; C494384:manganite