Abstract
Using light irradiation to manipulate magnetization over a prolonged period of time offers a wealth of opportunities for spin-based electronics and photonics. To date, persistent photomagnetism has been frequently reported in spin systems composed of molecular magnets; yet this phenomenon is rarely observed in nanoparticle-based systems comprised of transition metal oxides. Here, detailed studies of persistent photomagnetism in superparamagnetic iron oxide (Fe3O4) nanoparticles at temperatures below their blocking temperature are presented and it is demonstrated that the magnetization change does not occur through steady-state spin transitions or photothermal heating. Instead, it is found that exciton–spin exchange-coupling plays a critical role in modulating the magnetization by lowering the anisotropic energy barrier of Fe3O4 nanoparticles to facilitate their optically driven conversion from ferrimagnetic to superparamagnetic. Collectively, these insights establish a comprehensive understanding of the underlying photophysical processes that regulate photomagnetism in nanoparticle-based magnetic systems composed of transition metal oxides.
| Original language | English |
|---|---|
| Article number | 1700661 |
| Journal | Advanced Electronic Materials |
| Volume | 4 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 2018 |
Funding
This work was supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-0304. The authors also thank the National Science Foundation for support under Grant CHE-1308644 and the CCI Center for Nanostructured Electronic Materials (CHE-1038015). Materials characterization was conducted at the Major Analytical Instrumentation Center (MAIC) and the Nanoscale Research Facility (NRF), College of Engineering Research Service Centers, University of Florida. XPS characterization was conducted using an instrument purchased with NSF grant MRI-DMR1126115. The authors also thank Prof. Shuzhou Li from Nanyang Tech University for facilitating with the theoretical simulations. The SQUID measurement and TR-PL measurement of this research were conducted at the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory under User Proposal CNMS2014-111, CNMS2015-110, and CNMS2017-25, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
| Funders | Funder number |
|---|---|
| CCI Center for Nanostructured Electronic Materials | CHE-1038015 |
| Nanoscale Research Facility | |
| Office of Basic Energy Sciences | |
| Scientific User Facilities Division | |
| National Science Foundation | MRI-DMR1126115, CHE-1308644 |
| U.S. Department of Energy | |
| Air Force Office of Scientific Research | FA9550-14-1-0304 |
| Oak Ridge National Laboratory | CNMS2015-110, CNMS2017-25, CNMS2014-111 |
| University of Florida |
Keywords
- exchange-coupling
- excitons
- magnetic phase transition
- nanoparticlesphotomagnetism
- superparamagnetism
- transition metal oxides