Dramatic suppression of antiferromagnetic coupling in nanoparticle CuO

Magnetic susceptibility and muon spectroscopy measurements are carried out on antiferromagnetic nanoparticles (AFN) of CuO that are directly prepared by ball-milling a single crystal. The recently reported ferromagnetic features in AFN CuO of sol–gel growth are confirmed. New and significant result of the present work is a direct observation of an unusual dramatic reduction of the antiferromagnetic transition temperature, TN, from the bulk TN=230 to 50 K in AFN CuO by the μSR measurement.