Magnetic disorder in TbAl2 nanoparticles
| Autor: | Rojas Pupo, Daniel, Fernández Barquín, L., Sánchez Marcos, J., Echevarria-Bonet, C., Espeso, J.I., Rodríguez Fernández, J., Rodríguez Fernández, L., Mathon, M.H. |
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| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: | |
| Zdroj: | Materials Research Express, ISSN 2053-1591, 2015-07, Vol. 2, No. 7 Archivo Digital UPM Universidad Politécnica de Madrid |
| Popis: | The magnetic and thermal properties of TbAl2 nanosized alloys (diameters, 12 nm $\leqslant D\leqslant $ 20 nm) obtained by high-energy milling are characterised by specific heat, magnetisation and neutron scattering. The specific heat shows that the λ-anomaly at Curie temperature vanishes when the milling time reaches 300 h and its field variation shows a broad peak around 70 K disclosing a disordered magnetic state. The thermal variation of magnetization follows a Bloch process with a decrease of the stiffness constant and a faster demagnetisation with a quadratic exponent instead of the bulk ordinary ${T}^{3/2}$-dependence. The magnetic moment reduction in the nanosized alloys follows a 1/D dependence, remarking the role of disordered moment surface. The Rietveld analysis of the neutron diffraction patterns indicates a collinear ferromagnetic structure, with a reduction of the Tb-magnetic moment when decreasing the particle size. The temperature dependent overall magnetic signal of nanoparticles is derived from small-angle neutron scattering. A magnetic nanoparticle structure with an ordered ferromagnetic core and a disordered surface layer is proposed. |
| Databáze: | OpenAIRE |
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