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- Upadhyay, R. V., et al.
(author)
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Effect of rare-earth Ho ion substitution on magnetic properties of Fe3O4 magnetic fluids
- 2006
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 99:8
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Journal article (peer-reviewed)abstract
- Rare-earth atoms play an important role in determining the magnetocrystalline anisotropy in 4f-3d intermetallic compounds. Recently we reported on the synthesis and magnetic properties of Gd-substituted Mn-Zn ferrite nanoparticles as potentially suitable for magnetic fluid hyperthermia (MFH). In MFH the specific power absorption rate is related to the lossy magnetocrystalline anisotropic properties of the magnetic fluids. In this paper we report the role of Ho substitution in magnetite nanoparticles, which is found to enhance the KV product arising from the large anisotropy of Ho3+ moments. The zero-field-cooled magnetization data is then simulated by assuming noninteracting magnetic particles with uniaxial anisotropy and lognormal particle size distribution. The fit parameters give the values of particle diameter (D) 9 nm, standard deviation 0.3 in ln(D), and the anisotropy constant K to be 3.5x10(4) J/m(3). The value of K thus obtained is an order of magnitude larger than the value known for the undoped for magnetite (10(4) J/m(3)).
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| 2. |
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| 3. |
- Gupta, Amita, et al.
(author)
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Room temperature ferromagnetism in transition metal (V, Cr, Ti) doped In(2)O(3)
- 2007
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:9, s. 09N513-
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Journal article (peer-reviewed)abstract
- Indium oxide is chosen as the host material for doping Ti, V, and Cr transition metal ions. Theoretical calculations based on density functional theory within a local spin density approximation show that V-V separation of 5.6 A is more stable with a strong ferromagnetic coupling. Our calculations clearly predict that substitution of vanadium for indium should yield ferromagnetism in In(2)O(3). Experimentally, (In(0.95)TM(0.05))O(3) (TM=Ti,V,Cr) were prepared using sol-gel as well as solid state reaction methods. Superconducting quantum interference device magnetization measurements as a function of field and temperature clearly showed that the V and Cr doped samples are ferromagnetic with Curie temperature well above room temperature. Thin films deposited by pulsed laser ablation using these materials on sapphire substrates exhibit a preferred 222 orientation normal to the plane of the film. The magnetic moment for (In(0.95)V(0.05))O(3) film deposited in 0.1 mbar oxygen pressure was estimated to be 1.7 mu(B)/V and is comparable to the theoretical value of 2 mu(B)/V.
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