Spin-Polarization Transfer in Colloidal Magnetic-Plasmonic Au/Iron Oxide Hetero-nanocrystals

Abstract

We report on the unprecedented direct observation of spin-polarization transfer across colloidal magneto-plasmonic Au@Fe-oxide core@shell nanocrystal heterostructures. A magnetic moment is induced into the Au domain when the magnetic shell contains a reduced Fe-oxide phase in direct contact with the noble metal. An increased hole density in the Au states suggested occurrence of a charge-transfer process concomitant to the magnetization transfer. The angular to spin magnetic moment ratio, m(orb)/m(spin), for the Au 5d states, which was found to be equal to 0.38, appeared to be unusually large when compared to previous findings. A mechanism relying on direct hybridization between the Au and Fe states at the core/shell interface is proposed to account for the observed transfer of the magnetic moment.

Engineered inorganic core/shell nanoparticles

“…The transfer of spin-polarization from iron oxide into gold was evidenced in Au@Fe-oxide NPs, which constitutes the unique report of an induced magnetic moment transferred from a transition-metal oxide into a non-magnetic metal [204]. Synergetic effects from the combination of gold with oxide materials were also reported in the field of catalysis, but are still a matter of conditions.…”

Exchange bias effect in Au-Fe3O4nanocomposites

“…7,9 Recent reports have shown evidence of direct interaction due to spin polarization transfer between the magnetic moment and the non-magnetic plasmonic counterpart, thereby inducing finite magnetization in Au. 4 Simultaneously, it has been reported that the magnetic properties of Fe 3 O 4 are influenced due to the presence of Au in direct contact, which is evidenced as exchange bias (EB) effect, modified magnetization response to alternating fields, enhanced blocking temperature etc. 8,10 The EB effect in nanostructures has been an area of intense research over the last few decades.…”

Colloidal Magnetic Heterostructured Nanocrystals with Asymmetric Topologies: Seeded-Growth Synthetic Routes and Formation Mechanisms

“…In addition, while a metal or semiconductor domain can enable optical detection (e.g., via excitonic or LSPR absorption, or photoluminescence), a magnetic module can be utilized for complementary purposes, such as for magnetic resonance imaging (MRI), optical imaging, and magnetic separation (Choi et al, , 2008Jun et al, 2007;Jiang et al, 2008;Xu et al, 2008;Gao et al, 2009;Schladt et al, 2010;Bigall et al, 2012;Lim and Majetich, 2013). The existence of bonding heterointerfaces through which dissimilar materials can electronically communicate has clearly been recognized to impact on the magnetic (Xu et al, 2008;Lee et al, 2010a;Umut et al, 2012;Pineider et al, 2013;Kim and Song, 2014;Schick et al, 2014;López-Ortega et al, 2015;Velasco et al, 2015), optical (Levin et al, 2009;Korobchevskaya et al, 2011;Comin et al, 2012), transport (Lee et al, 2010a), magneto-optical Armelles et al, 2013), (electro)catalytic (Yin et al, 2008;Wang et al, 2009aWu et al, 2009;Lee et al, 2010b;George et al, 2011aGeorge et al, , 2013Jang et al, 2011b;Lin and Doong, 2011;Chen et al, 2012;Sun et al, 2012), and energy-storing properties of appropriately engineered MHNCs . Examples of MHNCs derived from heterogeneous deposition pathways are collected in Figures 2B-Q.…”

“…For example, MHNCs based on optically active semiconductors and/or noble metals supporting localized surface plasmon resonances (LSPRs) may exhibit anomalous absorption/emission and/or conductivity behavior due to modifications in electronic structure, degree of carrier confinement, recombination, separation and relocation dynamics of photostimulated charges carriers, and/or LSPR-to-exciton coupling (de Mello Donegà, 2011;He et al, 2013;Sitt et al, 2013;Banin et al, 2014;Melinon et al, 2014). In the case of MHNCs embodying magnetic phases and plasmonic metals, abnormally modified or mutually switchable magnetic, optical, and magneto-optical responses may reflect the synergistic interplay of magnetism, magneto-optical activity, and LSPR oscillations through various exchange-coupling mechanisms Jun et al, 2007;Casavola et al, 2008;Carbone and Cozzoli, 2010;Armelles et al, 2013;Pineider et al, 2013;López-Ortega et al, 2015). The possibility of achieving favorable electronic-structure hybridization at the heterointerfaces and of programing chargecarrier destination pathways across interfacial potential barriers of tunable height and widths in HNCs holds great fundamental and practical implications for (photo)catalytic, electrocatalytic, and chemical-sensing applications (Wang et al, 2009c;Costi et al, 2010;Chng et al, 2013;He et al, 2013;Rawalekar and Mokari, 2013;Banin et al, 2014;Song, 2015;Liao et al, 2016).…”