The exchange bias (EB) effect has been studied in Ni/NiO nanogranular samples obtained by annealing in H2, at different temperatures (200 £ Tann £ 300 °C), NiO powder previously ball-milled for 20 hours. Typically, the samples consist of Ni nanoparticles (mean size of 10-18 nm) embedded in a nanocrystalline NiO matrix. With increasing Tann, the Ni fraction varies from 4 % up to 69 %. The exchange field depends on the Ni amount, being maximum (~ 600 Oe), at T = 5 K, in the sample with 15 % Ni. In all the samples, the EB effect vanishes at T = 200 K. The structural features of the samples have been investigated by X-ray diffraction, electron microscopy and extended X-ray absorption fine structure and the low-temperature magneto-thermal behaviour has been thoroughly analyzed. The results show the existence of a structurally and magnetically disordered NiO component, which plays the key role in the EB mechanism.
Exchange bias and interface structure in the Ni/NiO nanogranular system / L. Del Bianco; F. Boscherini; M. Tamisari; F. Spizzo; M. Vittori Antisari; E. Piscopiello. - In: JOURNAL OF PHYSICS. D, APPLIED PHYSICS. - ISSN 1361-6463. - STAMPA. - 41:(2008), pp. 134008-134008-7. [10.1088/0022-3727/41/13/134008]
Exchange bias and interface structure in the Ni/NiO nanogranular system
DEL BIANCO, LUCIA;BOSCHERINI, FEDERICO;
2008
Abstract
The exchange bias (EB) effect has been studied in Ni/NiO nanogranular samples obtained by annealing in H2, at different temperatures (200 £ Tann £ 300 °C), NiO powder previously ball-milled for 20 hours. Typically, the samples consist of Ni nanoparticles (mean size of 10-18 nm) embedded in a nanocrystalline NiO matrix. With increasing Tann, the Ni fraction varies from 4 % up to 69 %. The exchange field depends on the Ni amount, being maximum (~ 600 Oe), at T = 5 K, in the sample with 15 % Ni. In all the samples, the EB effect vanishes at T = 200 K. The structural features of the samples have been investigated by X-ray diffraction, electron microscopy and extended X-ray absorption fine structure and the low-temperature magneto-thermal behaviour has been thoroughly analyzed. The results show the existence of a structurally and magnetically disordered NiO component, which plays the key role in the EB mechanism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
