Influence of Al3+ doping on the magnetism of one-dimensional frustrated Ca3CoMnO6 compound
Previous reports depict that the nonstoichiometric Co/Mn ratio greatly affects the physical properties of Ca 3 CoMnO 6 , but few papers focus on the Co/Mn site doping effect. In order to investigate the influence of the substitution on the magnetization, partial Mn 4+ ions were replaced with Al 3+ ions and polycrystalline Ca 3 CoMn 1- x Al x O 6 ( x = 0, 0.05, 0.1, 0.15, 0.2) samples were prepared. All the samples crystallized into rhombohedral structure without existence of impurities. SEM patterns showed that the mean particle size decreased with the introduction of Al element. Due to the dilution effect of nonmagnetic Al 3+ ions to the spin chains, the competing short-range antiferromagnetic/ferromagnetic order caused by the “order by disorder” phenomenon was suppressed. The high-temperature spin freezing peak disappeared gradually and the doped samples presented a faster dynamic behavior, indicating a more robust long-range antiferromagnetic order. The time-dependent magnetization showed a nonmonotonic relaxation in a field of 5T, implying the possible existence of quantum tunneling of magnetization. Ca 3 CoMn 1- x Al x O 6 ( x = 0, 0.05, 0.1, 0.15, 0.2) samples were synthesized and all of them crystallized into single-phase rhombohedral structure. Due to the dilution effect of the nonmagnetic Al 3+ ions to the …Co 2+ -Mn 4+ -Co 2+ -Mn 4+ …spin chains, the high-temperature spin freezing peak disappears gradually and a faster dynamic behavior in the doped samples is observed. Our investigation confirms that the substitution of the nonmagnetic Al 3+ ions has a similar effect with the Co/Mn defection. This is to say that the nonmagnetic doping could also suppress the formation of short-range magnetic correlation and help in building a more robust long-range antiferromagnetic order. For the nonmonotonic relaxation of the time-dependent magnetization, it implies the possible existence of quantum tunneling of magnetization. The normalized time-dependent M/M 0 curves for Ca 3 CoMn 1- x Al x O 6 ( x = 0, 0.05, 0.1, 0.15, 0.2) measured at 5 K. (1) The magnetization was measured by cooling the samples down to 5K, a field of 5T was applied and kept for 10 min, switching off the field and the remanent magnetization was recorded. (2) The magnetization was measured by cooling the samples down to 5 K firstly and the magnetic field was switched on, as well as field reaches 5T the magnetization was recorded immediately.
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