2 research outputs found
Spin reversal and magnetization jumps in ErMexMn1 xO3 perovskites (Me ¼ Ni, Co)
The erbium-based manganite ErMnO3 has been partially substituted at the manganese site by the transition-metal elements Ni and Co.
The perovskite orthorhombic structure is found from x(Ni) ¼ 0.2–0.5 in the nickel-based solid solution ErNixMn1 xO3, while it can be
extended up to x(Co) ¼ 0.7 in the case of cobalt, provided that the synthesis is performed under oxygenation conditions to favor the
presence of Co3+. Presence of different magnetic entities (i.e., Er3+, Ni2+, Co2+, Co3+, Mn3+, and Mn4+) leads to quite unusual
magnetic properties, characterized by the coexistence of antiferromagnetic and ferromagnetic interactions. In ErNixMn1 xO3, a critical
concentration xcrit(Ni) ¼ 1/3 separates two regimes: spin-canted AF interactions predominate at xoxcrit, while the ferromagnetic
behavior is enhanced for x4xcrit. Spin reversal phenomena are present both in the nickel- and cobalt-based compounds. A
phenomenological model based on two interacting sublattices, coupled by an antiferromagnetic exchange interaction, explains the
inversion of the overall magnetic moment at low temperatures. In this model, the ferromagnetic transition-metal lattice, which orders at
Tc, creates a strong local field at the erbium site, polarizing the Er moments in a direction opposite to the applied field. At low
temperatures, when the contribution of the paramagnetic erbium sublattice, which varies as T 1, gets larger than the ferromagnetic
contribution, the total magnetic moment changes its sign, leading to an overall ferrimagnetic state. The half-substituted compound
ErCo0.50Mn0.50O3 was studied in detail, since the magnetization loops present two well-identified anomalies: an intersection of the
magnetization branches at low fields, and magnetization jumps at high fields. The influence of the oxidizing conditions was studied in
other compositions close to the 50/50 ¼ Mn/Co substitution rate. These anomalies are clearly connected to the spin inversion
phenomena and to the simultaneous presence of Co2+ and Co3+ magnetic moments. Dynamical aspects should be considered to well
identify the high-field anomaly, since it depends on the magnetic field sweep rate.Peer reviewe
Spin reversal and magnetization jumps in ErMexMn1-xO3 perovskites (Me = Ni, Co)
J. Magn. Magn. Mat., 2007, 312, 78-9