Pressure induced insulator–metal transition and giant negative piezoresistance in Pr0.6Ca0.4Mn0.96Al0.04O3 polycrystal

Abstract The effect of external hydrostatic pressure ( P ) on the magnetization ( M ) and resistivity ( ρ ) properties of charge-orbital (CO) ordered-insulating phase-separated manganite Pr 0.6 Ca 0.4 Mn 0.96 Al 0.04 O 3 system is reported here. At ambient P , CO ordering transition and spin-canting in the AFM are observed at 223 K and 55 K respectively in M ( T ) and ρ ( T ) measurements. Application of P increases simultaneously the magnitude of magnetization ( M ) and transition temperature, and weakens the CO ordering in M ( T ) measurements up to 0.98 GPa. During ρ ( T ) measurements, P induces an insulator–metallic transition ( T IM ) at 1.02 GPa, and further increase of P up to 2.84 GPa leads to increase of T IM (d T IM /d P =21.6 K/GPa). ρ at T IM is reduced about three orders of magnitude at 2.84 GPa, and leads to the giant negative piezoresistance (~98%). These results are analyzed separately in two temperature regions i.e., below and above T IM by power function equation and small polaronic hopping model respectively. It is understood from these analyses that the application of P suppresses the Jahn–Teller distortions, electron–electron and electron–magnon scattering factors, and induces the insulator–metal transition in Pr 0.6 Ca 0.4 Mn 0.96 Al 0.04 O 3 system.