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FMR Study of Co/Ti Bilayer Thin Films

100%

Erkovan M., Tokdemir Öztürk S., Taşkın Gazioğlu D., Topkaya R., Öztürk O.

Acta Physica Polonica A

2014

vol. 125

issue 2

673-676

We focused on the interaction between two ferromagnetic cobalt layers through a non-magnetic titanium layer. The magnetic properties of the structure were characterized by ferromagnetic resonance technique. The data were collected as a function of non-magnetic titanium layer thickness. Co/Ti multilayer (Ti(50 Å)/Co(45 Å)/Ti(2-40 Å)/Co(40 Å)/Ti(100 Å)) films were grown onto naturally oxidized p-type single crystal Si (100) substrate at UHV condition with magnetron sputtering system at room temperature. The thickness of Ti spacer layer ranges from 2 to 40 Å with 2 Å steps. We did not observe usual optic and acoustic modes; instead we had two broad overlapped peaks for the films ranged from 6 Å to 40 Å. One interesting result was the high anisotropic resonance field values for these films. Exchange coupling between ferromagnetic layers causes shift on resonance field values but these shifts in our samples were much larger than expected. This large anisotropic behavior is not clear at the moment. Our theoretical model was not able to determine a value for the exchange coupling parameter. One reason can be the close thickness values for Co sublayers. The other reason can be the Ti non-magnetic layer. If titanium did not grow layer by layer on cobalt, the cobalt ferromagnetic layers may behave as a single layer. As a result one cannot observe exchange interaction between ferromagnetic layers through non-magnetic spacer.

The Effect of Milling Time and Sintering Temperature on Crystallization of BaFe₁₂O₁₉ Phase and Magnetic Properties of Ba-Hexaferrite Magnet

73%

Sadullahoğlu G., Ertuğ B., Gökçe H., Altuncevahir B., Öztürk M., Topkaya R., Akdoğan N., Öveçoğlu M., Addemir O.

Acta Physica Polonica A

2015

vol. 128

issue 3

377-382

Barium hexaferrite samples were prepared by mechanical alloying using the stoichiometric amounts of BaCO₃ and Fe₂O₃ precursors followed by heat treatment applied in the temperature range 700-1150°C. It was found that the high energy ball mill with a milling rate enabled to obtain powders with the finer particles at the reduced milling time mechanical alloying of the initial powders linked to the formation of barium hexaferrite phase. The exothermic reaction peaks corresponding to the formation of BaFe₁₂O₁₉ phase shift from 928°C to 793°C for the increased milling time up to 6 h. This was resulted in improved magnetic properties that the Mₛ value of the as-blended sample sintered at 800°C rised from 31.16 emu/g to 53.46 emu/g after milling for 6 h. The saturation magnetization and remanence values of the samples mechanically alloyed for 3 h and sintered at 1150°C also increased to 63.57 emu/g and 31.26 emu/g, respectively, more than for 800°C and 900°C. The increase in the annealing temperature favours the formation of BaFe₁₂O₁₉ phase in the samples.

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2 Acta Physica Polonica A

1 2015

1 2014

2 Topkaya R.

1 Addemir O.

1 Akdoğan N.

1 Altuncevahir B.

1 Erkovan M.

1 Ertuğ B.

1 Gökçe H.

1 Sadullahoğlu G.

1 Taşkın Gazioğlu D.

1 Tokdemir Öztürk S.

1 Öveçoğlu M.

1 Öztürk M.

1 Öztürk O.

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FMR Study of Co/Ti Bilayer Thin Films

The Effect of Milling Time and Sintering Temperature on Crystallization of BaFe₁₂O₁₉ Phase and Magnetic Properties of Ba-Hexaferrite Magnet