DC and AC Magnetization Study of Complex Ilmenite Oxides (Ni1-xCox)TiO3   (0.05 < x < 0.8)
  Ilmenite solid-solutions, (Ni1-xCox)TiO3 (0.05 < x < 0.8), were synthesized at ambient atmosphere through solid-state reaction and were studied by energy dispersive spectroscopy of X-rays, X-ray diffraction, and DC and AC magnetometry. Temperature dependent DC magnetic measurements revealed two transitions. The first took place at around 27 K and the second at 63 K. The low-temperature phase was antiferromagnetic. The phase observed between 27 and 63 K is characteristic to the solid-solution and is not found in either of the constituent members. A fit of the data to the Curie-Weiss law gave magnetic moment values which were significantly larger than the values based on the quenched orbital momentum assumption. Zero-field-cooled magnetization measurements with weak magnetic field revealed unexpected negative magnetization at low temperatures. Below 63 K the DC magnetization exhibited time dependent behavior. Frequency and magnetic field dependent AC magnetization is also addressed. 
Yukari Fujioka and Johannes Frantti
cond-mat.str-el