Emergent Magnetic State in (111)-Oriented Quasi-Two-Dimensional Spinel Oxides.
We report on the emergent magnetic state of (111)-oriented CoCr2O4 ultrathin films sandwiched between Al2O3 spacer layers in a quantum confined geometry. At the two-dimensional crossover, polarized neutron reflectometry reveals an anomalous enhancement of the total magnetization compared to the bulk value. Synchrotron X-ray magnetic circular dichroism measurements demonstrate the appearance of a long-range ferromagnetic ordering of spins on both Co and Cr sublattices. Brillouin function analyses and ab-initio density functional theory calculations further corroborate that the observed phenomena are due to the strongly altered magnetic frustration invoked by quantum confinement effects, manifested by the onset of a Yafet-Kittel-type ordering as the magnetic ground state in the ultrathin limit, which is unattainable in the bulk.
['Liu|Xiaoran|X|0000-0003-0938-6109', 'Singh|Sobhit|S|', 'Kirby|Brian J|BJ|', 'Zhong|Zhicheng|Z|0000-0003-1507-4814', 'Cao|Yanwei|Y|', 'Pal|Banabir|B|', 'Kareev|Mikhail|M|', 'Middey|Srimanta|S|0000-0001-5893-0946', 'Freeland|John W|JW|', 'Shafer|Padraic|P|0000-0001-9363-2557', 'Arenholz|Elke|E|', 'Vanderbilt|David|D|', 'Chakhalian|Jak|J|']
magnetism Spinels ultrathin films emergent properties