Size-induced Exchange Bias in Single-phase CoO Nanoparticles
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arXiv
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| Autores principales: | , , , , , |
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| Formato: | Preprint |
| Publicado: |
2024
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| _version_ | 1866913311980781568 |
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| author | Sharma, Vikash Pal, Sudip Sharma, Divya Shukla, Dinesh Kumar Chaudhary, Ram Janay Okram, Gunadhor Singh |
| author_facet | Sharma, Vikash Pal, Sudip Sharma, Divya Shukla, Dinesh Kumar Chaudhary, Ram Janay Okram, Gunadhor Singh |
| contents | We report exchange bias (EB) in single-phase CoO nanoparticles, where two magnetic phases naturally emerge as the crystallite size decreases from 34.6 to 10.8 nm. The Néel temperature (TN) associated with antiferromagnetic ordering decreases monotonically with the reduction in crystallite size, highlighting the significant influence of size effects. The 34.6 nm nanoparticles exhibit magnetization irreversibility between zero field cooled (ZFC) and field-cooled (FC) states below TN. This irreversibility appears well above TN with further reduction in size, resulting in the absence of true paramagnetic regime which indicates the occurrence of an additional magnetic phase. The frequency-dependent ac-susceptibility in 10.8 nm nanoparticles suggests slow dynamics of disordered surface spins above TN, coinciding with the establishment of long-range order in the core. The thermoremanent magnetization (TRM) and isothermoremanent magnetization (IRM) curves suggest a core-shell structure: the core is antiferromagnetic, and the shell consists of disordered surface spins causing ferromagnetic interaction. Hence, the exchange bias in these CoO nanoparticles results from the exchange coupling between an antiferromagnetic core and a disordered shell that exhibits unconventional surface spin characteristics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_06876 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Size-induced Exchange Bias in Single-phase CoO Nanoparticles Sharma, Vikash Pal, Sudip Sharma, Divya Shukla, Dinesh Kumar Chaudhary, Ram Janay Okram, Gunadhor Singh Mesoscale and Nanoscale Physics We report exchange bias (EB) in single-phase CoO nanoparticles, where two magnetic phases naturally emerge as the crystallite size decreases from 34.6 to 10.8 nm. The Néel temperature (TN) associated with antiferromagnetic ordering decreases monotonically with the reduction in crystallite size, highlighting the significant influence of size effects. The 34.6 nm nanoparticles exhibit magnetization irreversibility between zero field cooled (ZFC) and field-cooled (FC) states below TN. This irreversibility appears well above TN with further reduction in size, resulting in the absence of true paramagnetic regime which indicates the occurrence of an additional magnetic phase. The frequency-dependent ac-susceptibility in 10.8 nm nanoparticles suggests slow dynamics of disordered surface spins above TN, coinciding with the establishment of long-range order in the core. The thermoremanent magnetization (TRM) and isothermoremanent magnetization (IRM) curves suggest a core-shell structure: the core is antiferromagnetic, and the shell consists of disordered surface spins causing ferromagnetic interaction. Hence, the exchange bias in these CoO nanoparticles results from the exchange coupling between an antiferromagnetic core and a disordered shell that exhibits unconventional surface spin characteristics. |
| title | Size-induced Exchange Bias in Single-phase CoO Nanoparticles |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2404.06876 |