Effect of doping on the magnetic properties of the low-dimensional antiferromagnet CuO

Magnetic properties of mechanically milled nanosized cupric oxide

“…The augment in magnetization with the milling time is likely due to an enhancement in moment uncompensation in the antiferromagnet because of the increase in the surface-to-volume ratio as well as the presence of crystal defects generated by the grinding. The moment enhancement is also reported for systems with oxygen vacancies [17], systems with magnetic and nonmagnetic doping [4,18], and sol-gel derived CuO nanoparticles [10]. This residual magnetization was assigned by Arbuzova et al [14] to a noncollinear ordering and by Azzoni et al [19] to weak ferromagnetism.…”

“…The inverse dependence of susceptibility on temperature for To65 K is an unexpected feature in the behavior of wðTÞ of CuO. This increase was believed to be caused by Cu 3+ ions appearing due to the presence of cation vacancies, or related to the frustration of interaction in long-range order regions of CuO or is due to paramagnetic surface layers [4,14,15]. As noted by Arbuzova et al [4,15], defects affect the magnetic long and short ordering in CuO.…”

“…Further, the difference between the maximum and minimum value of w; Dw; decreases with the milling time. A decrease in Dw due to an increase in the point defect population has also been noted in heat-treated polycrystalline and single crystal samples [4]. Typical magnetic isotherms for the 30 and 50 h milled samples are shown in Fig.…”

“…This increase was believed to be caused by Cu 3+ ions appearing due to the presence of cation vacancies, or related to the frustration of interaction in long-range order regions of CuO or is due to paramagnetic surface layers [4,14,15]. As noted by Arbuzova et al [4,15], defects affect the magnetic long and short ordering in CuO. The shape of the susceptibility curve for the milled samples is the evidence of the fact that both long-and short-range ordering in CuO are affected upon prolonged milling.…”

“…Over and above, the study of CuO by itself is essential since many of its magnetic properties are governed by the oxygen stoichiometry. The diverse results obtained by different authors when measuring its magnetic properties have been attributed to the existence of intrinsic defects like cation or anion vacancies [4,5], particle size effects [6], and uncompensated charges [4].…”