Journal of Advanced Chemical Engineering

Magnetism in metal-free phthalocyanine and graphite-like nanostructures

2^nd World Congress on Biopolymers

August 04-05, 2016 Manchester, UK

Armen N Kocharian, Eduard Sharoyan, Armen Mirzakhanyan, Harutyun Gyulasaryan, Carlos Sanchez, Oscar Bernal, Aram Manukyan and Michail C Goff

California State University, USA
National Academy of Sciences of Armenia, Armenia

Scientific Tracks Abstracts: J Adv Chem Eng

Abstract:

From the point of view of both fundamental science and practical applications, of great interest is high-temperature ferromagnetism, observed in various carbon-based materials. Carbon microspheres with interesting magnetic properties have been fabricated by the solid-phase pyrolysis of a metal-free phthalocyanine H2Pc=H2(C32N8H16) used as a precursor. By changing the conditions of pyrolysis, we prepared carbon microspheres with a mean diameter 2-3.8 μm consisting of (layered graphite) graphitized nanocrystallites and amorphous carbon with a thickness of 5-15 graphene layers and width of 5-20 nm and sufficiently narrow size distribution. In particular, at Tpyr=700°C and tpyr=30 min, we obtained carbon microspheres with a mean diameter d=3.4±0.15 μm. The comparison of magnetic properties in metal-free phthalocyanine and graphite-like nanostructures is provided in the broad range of temperatures and magnetic fields. Magnetic characteristics of these samples were investigated with a vibrational magnetometer in the temperature range 5-300 �?, as well as with electron spin resonance (ESR) spectroscopy. Analysis of curves �?-Т and �?-Н shows the presence of paramagnetic centers with the concentration n=3�??1019 spin/g and temperature-independent diamagnetism with susceptibility of �?Dia=1.2�??10-6 emu/g�??Oe. The parameters of ESR spectrum were measured at 300K: the g-factor 2.0031 and intensity ~5�??1019 spin/g. The ESR line width is only 0.8 Oe which indicates a strong exchange narrowing. Along with the paramagnetic centers and diamagnetism, we have revealed ferromagnetic hysteresis loops from T=5 K to room temperature. The dependences of magnetizations of diamagnetic and ferromagnetic signal on H at T=300K are presented in figures below. The maximum value of coercive force is 150 Oe at T=300K. We also analyze the nature of the reported evidence on superparamagnetism, diamagnetism and ferromagnetic ordering in the metalfree phthalocyanine and metal-free pyrolytic carbon structures containing only p- and s-electrons.

Biography :

Armen N Kocharian has an expertise in the field of magnetism and electron instabilities in low dimensional systems. He has completed his PhD at the Moscow State University in Moscow, 1977 and DSc in Yerevan Physics Institute, 1991. He has published more than 125 papers in reputed journals. He is a Member of Editorial Board of the International J. on ISRN Condensed Matter (2011), Peer reviewer in Materials Letters (2015), J. Magn. & Magn. Materials (2015), Phys. Chemistry Chemical Physics (2014), RSC Advances (2014), J. of Nanoparticle Research (2012).

Email: armen.kocharian@calstatela.edu