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Goswami S, Gupta P, Nayak S, Bedanta S, Iglesias Ò, Chakraborty M, De D. Dependence of Exchange Bias on Interparticle Interactions in Co/CoO Core/Shell Nanostructures. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3159. [PMID: 36144947 PMCID: PMC9502722 DOI: 10.3390/nano12183159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 09/04/2022] [Accepted: 09/07/2022] [Indexed: 06/16/2023]
Abstract
This article reports the dependence of exchange bias (EB) effect on interparticle interactions in nanocrystalline Co/CoO core/shell structures, synthesized using the conventional sol-gel technique. Analysis via powder X-Ray diffraction (PXRD) studies and transmission electron microscope (TEM) images confirm the presence of crystalline phases of core/shell Co/CoO with average particle size ≈ 18 nm. Volume fraction (φ) is varied (from 20% to 1%) by the introduction of a stoichiometric amount of non-magnetic amorphous silica matrix (SiO2) which leads to a change in interparticle interaction (separation). The influence of exchange and dipolar interactions on the EB effect, caused by the variation in interparticle interaction (separation) is studied for a series of Co/CoO core/shell nanoparticle systems. Studies of thermal variation of magnetization (M-T) and magnetic hysteresis loops (M-H) for the series point towards strong dependence of magnetic properties on dipolar interaction in concentrated assemblies whereas individual nanoparticle response is dominant in isolated nanoparticle systems. The analysis of the EB effect reveals a monotonic increase of coercivity (HC) and EB field (HE) with increasing volume fraction. When the nanoparticles are close enough and the interparticle interaction is significant, collective behavior leads to an increase in the effective antiferromagnetic (AFM) CoO shell thickness which results in high HC and HE. Moreover, in concentrated assemblies, the dipolar field superposes to the local exchange field and enhances the EB effect contributing as an additional source of unidirectional anisotropy.
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Affiliation(s)
- Suchandra Goswami
- Material Science Research Lab, The Neotia University, Sarisa, D.H. Road, 24 Pgs (South), Sarisha 743368, West Bengal, India
| | - Pushpendra Gupta
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni 752050, India
| | - Sagarika Nayak
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni 752050, India
| | - Subhankar Bedanta
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni 752050, India
- Center for Interdisciplinary Sciences (CIS), National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni 752050, India
| | - Òscar Iglesias
- Department Física de la Matèria Condensada and IN2UB, Facultat de Física, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
| | - Manashi Chakraborty
- Material Science Research Lab, The Neotia University, Sarisa, D.H. Road, 24 Pgs (South), Sarisha 743368, West Bengal, India
| | - Debajyoti De
- Material Science Research Lab, The Neotia University, Sarisa, D.H. Road, 24 Pgs (South), Sarisha 743368, West Bengal, India
- Department of Physics, Sukumar Sengupta Mahavidyalaya, State Highway 7, Keshpur, Paschim Medinipur 721150, India
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