Influence of finite size and image charge screening on the antiferromagnetic ordering of CoO ultrathin films

Antiferromagnetism of CoO-NiO bilayers studied by XMLD spectroscopy

“…Such enhancement of T N is expected to be further increased for thinner CoO layers, resulting from the short-range nature of the interfacial exchange interactions. Although in the present study, we were unable to determine T N of the CoO layers using the LEED method [46] due to the insulating nature of the substrate, our studies on a similar system, CoO/NiO/Ag(001) have shown that the T N indeed increases with lowering of the CoO thickness [52], supporting the room temperature magnetism of the 2 ML CoO film coupled to NiO layers. Here we have assumed that the Co moments near the interface do not undergo any canting due to their high anisotropy compared to NiO.…”

“…However, looking at the Co XMLD in figure 2(a), we observe that there is little dichroism for the 2 ML CoO film, while the dichroism increases progressively for the 5 and 10 ML CoO layers, which is also observed in the variation of the CoO ∆R L3 (R 90 L3 − R 15 L3 ), shown in figure 2(c). The Co XMLD for 10 ML CoO film observed in figure 2(a) is smaller in magnitude than that observed by [29] as the present experiments were performed at RT against 78 K for Li et al Our recent studies have shown that the surface T N of CoO(001) ultrathin films on MgO(001) [43] and Ag(001) [46] depends on different parameters such as finite size, strain, substrate polarizability etc. The measured surface T N for CoO(001) films of 2, 5 and 10 ML thicknesses grown on 10 ML MgO film atop Ag(001) substrate is shown in figure 2(d) using a LEED-based method [43,46] while the bulk Néel temperature (T N ) of CoO is 291 K [46].…”

“…The Co XMLD for 10 ML CoO film observed in figure 2(a) is smaller in magnitude than that observed by [29] as the present experiments were performed at RT against 78 K for Li et al Our recent studies have shown that the surface T N of CoO(001) ultrathin films on MgO(001) [43] and Ag(001) [46] depends on different parameters such as finite size, strain, substrate polarizability etc. The measured surface T N for CoO(001) films of 2, 5 and 10 ML thicknesses grown on 10 ML MgO film atop Ag(001) substrate is shown in figure 2(d) using a LEED-based method [43,46] while the bulk Néel temperature (T N ) of CoO is 291 K [46]. We could not perform similar Néel temperature measurements for the present bilayer samples due to the sample charging effects mentioned earlier.…”

Multiplet effects in the electronic correlation of one-dimensional magnetic transition metal oxides on metals

“…The modeling of these magnetic properties is subject to understanding Coulomb interactions. As a matter of fact, a variation in the Curie and Néel critical temperatures has been observed during magnetic oxide film growth on metals that can be explained by the image potential screening length [30,31]. As a first approximation, the magnetic exchange along the chain follows from the electron hopping through X(d)-O(p)-X(d) orbitals (superexchange) [32,33].…”

Multiplet Effects in the Electronic Correlation of One-Dimensional Magnetic Transition-Metal Oxides on Metals

“…The modelling of these magnetic properties is subject to understanding Coulomb interactions. As a matter of fact, a variation in the Curie and Néel critical temperatures has been observed during magnetic oxide film growth on metals that can be explained by the image potential screening length [30,31]. As a first approximation, the magnetic exchange along the chain follows from the electron hopping through X(d)-O(p)-X(d) orbitals (superexchange) [32,33].…”