Ferromagnetic behavior of the Zn-Mn-O system

Abstract

Polycrystalline Zn-Mn-O samples with nominal manganese concentrations x = 0.01, 0.04 and 0.10 were synthesized by a solid state reaction route using (ZnC2O4?2H2O)1-x and (MnC2O4?2H2O)x. Thermal treatment of the samples was performed in air at temperatures 673, 773, 873, 973 and 1173 K for x = 0.01 and at the temperature 773 K for x = 0.04 and 0.10. The samples were investigated by X-ray diffraction, thermogravimetry, differential thermal analysis, transmission electron microscopy, magnetization measurements and electron paramagnetic resonance. X-Ray diffraction was also performed on MnO2 thermally treated at temperatures 673, 773, 873, 973, 1073 and 1173 K. Room temperature ferromagnetism was observed in the Zn-Mn-O samples with x = 0.01 thermally treated at low temperatures (673 and 773 K) and in the sample with x = 0.04 thermally treated at 773 K. It seems that the ferromagnetic phase could originate from interactions between Mn2+ and acceptor defects incorporated in the ZnO crystal lattice during the thermal treatment of the samples.Polikristalni uzorci Zn-Mn-O nominalnih koncentracija mangana x = 0,01, 0,04 i 0,10 dobijeni su reakcijom u cvstom stanju izmedju (ZnC2O4?2H2O)1-x i (MnC2O4?2H2O)x. Termicki tretman je izvrsen na vazduhu i temperaturama 673, 773, 873, 973 i 1173 K za x = 0,01 i na temperaturi 773 K za x = 0,04 i 0,10. Uzorci su ispitivani metodama difrakcije x-zraka na prahu, termogravimetrije, diferencijalne termalne analize, transmisione elektronske mikroskopije, merenja magnetizacije i elektronske paramagnetne rezonance. Metodom difrakcije x-zraka na prahu su ispitani i uzorci MnO2 termicki tretirani na temperaturama 673, 773, 873, 973, 1073 i 1173 K. Feromagnetizam na sobnoj temperaturi je uocen u Zn-Mn-O uzorcima koncentracije mangana x = 0,01 termicki tretiranim na niskim temperaturama (673 i 773 K) i u uzorku x = 0,04 termicki tretiranom na 773 K. Rezultati ukazuju na to da bi feromagnetizam mogao da bude posledica interakcije izmedju Mn2+ i akceptorskih defekata ugradjenih u kristalnu resetku ZnO za vreme termickog tretmana uzoraka.