Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 2 / 2
First pagePrevious page1Next pageLast page
1.
Effect of shell thickness on the exchange bias blocking temperature and coercivity in Co-CoO core-shell nanoparticles
Senoy Thomas, K. Reethu, Thanveer Thajudheen, M. T. Z. Myint, S. H. Al-Harthi, 2017, original scientific article

Abstract: The exchange bias blocking temperature distribution of naturally oxidized Co-CoO core-shell nanoparticles exhibits two distinct signatures. These are associated with the existence of two magnetic entities which are responsible for the temperature dependence of an exchange bias field. One is from the CoO grains which undergo thermally activated magnetization reversal. The other is from the disordered spins at the Co-CoO interface which exhibits spin-glass-like behavior. We investigated the oxide shell thickness dependence of the exchange bias effect. For particles with a 3 nm thick CoO shell, the predominant contribution to the temperature dependence of exchange bias is the interfacial spin-glass layer. On increasing the shell thickness to 4 nm, the contribution from the spin-glass layer decreases, while upholding the antiferromagnetic grain contribution. For samples with a 4 nm CoO shell, the exchange bias training was minimal. On the other hand, 3 nm samples exhibited both the training effect and a peak in coercivity at an intermediate set temperature Ta. This is explained using a magnetic core-shell model including disordered spins at the interface.
Keywords: exchange interactions, magnetic ordering, ferromagnetic materials, magnetic materials, polycrystalline material, thin films, nanoparticle, nuclear structure models, oxides, transition metals
Published in RUNG: 13.12.2024; Views: 324; Downloads: 2
URL Link to file
This document has many files! More...

2.
Magnetocaloric effect in amorphous and partially crystallized Fe[sub](40)Ni[sub](38)Mo[sub]4B[sub](18) alloys
Thanveer Thajudheen, R. V. Ramanujan, Senoy Thomas, 2016, original scientific article

Abstract: A study of magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys is reported. Amorphous Fe40Ni38Mo4B18, near its magnetic ordering temperature (600K) showed a magnetic entropy change ΔSM of 1.1 J/KgK and a relative cooling power of 36J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperature of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27J/kgK near the magnetic ordering temperature of the amorphous matrix (540K) in a field change of 10 kOe. The decrease in ΔSM on partial crystallisation is attributed to the biphasic magnetic nature of the s
Keywords: magnetism, phase transitions, entropy, equations of state, alloys, amorphous materials, annealing
Published in RUNG: 07.11.2024; Views: 421; Downloads: 3
.pdf Full text (3,13 MB)
This document has many files! More...

Search done in 0.01 sec.
Back to top