Transport and magnetic properties of sheet poly metallo phthalocyanines (poly M Pcs)(MCu, Ni)

Abstract

Measurements of dc electrical conductivity, σ, thermopower, S and magnetic susceptibility, χ on poly metallo phthalocyanines ([MPcs]_n) (MCu,Ni) before heat treatment (I[MPc]n) and after heat treatment (II[MPc]_n) are reported. σ at room temperature (RT) for I[MPc]_n is of the order of 10⁻⁹ (ohm.cm)⁻¹. σ at RT for II[CuPc]_n is 0.4 (ohm.cm)⁻¹ and drops by three orders of magnitude as the temperature is decreased to 50K while for II[NiPc]n, σ drops from 10⁻⁴ (ohm.cm)⁻¹ at RT to 5∗10⁻⁶ (ohm.cm)⁻¹ at 200K. S at 240K is 11microV/K for II[CuPc]_n and 105microV/K for II[NiPc]_n. Both the polymers have a positive thermopower in the temperature range of our measurements. The temperature dependence of σ is in accordance with that expected for variable range hopping of carriers in 3-dimensions (VRH 3D) for II[CuPc]_n and that expected for VRH of carriers in 2-dimensions (VRH 2D) for II[NiPc]_n. S varies linearly with temperature for II[NiPc]n. For II[CuPc]_n a sub-linear temperature dependence of S is observed. χ at 300K for I[NiPc]n is diamagnetic and for II[NiPc]_n is paramagnetic. χ at 300K for both I and II[CuPc]_n are paramagnetic. χ for both the II[MPc]_n are temperature independent from 350K down to 120K and show a Curie like behaviour at lower temperatures.