Wyniki wyszukiwania - BazTech

1

Magnetic properties of ZnO:Co layers obtained by pulsed laser deposition method

Stefaniuk I., Cieniek B., Rogalska I., Virt I. S., Kościak A.

Materials Science Poland

|

2018

|

Vol. 36, No. 3

439--444

EN

We have studied magnetic properties of zinc oxide (ZnO) composite doped with Co ions. The samples were obtained by pulsed laser deposition (PLD) method. Electron magnetic resonance (EMR) measurements were carried out and temperature dependence of EMR spectra was obtained. Analysis of temperature dependence of the integral intensity of EMR spectra was carried out using Curie-Weiss law. Reciprocal of susceptibility of an antiferromagnetic (AFM) material shows a discontinuity at the Néel temperature and extrapolation of the linear portion to negative Curie temperature. The results of temperature dependence of EMR spectra for the ZnO:Co sample and linear extrapolation to the Curie-Weiss law indicated the AFM interaction between Co ions characterized by the Néel temperatures TN = 50 K and TN = 160 K for various samples. The obtained g-factor is similar to g-factors of nanocrystals presented in literature, and the results confirm that in the core of these nanocrystals Co was incorporated as Co2+, occupying Zn2+ sites in wurtzite structure of ZnO.

2

EPR study of ZnO:Co thin films grown by the PLD method

Cieniek B., Stefaniuk I., Virt I.

Nukleonika

|

2013

|

Vol. 58, No. 3

359--363

EN

We have studied magnetic properties of zinc-oxide composite doped with a relatively high concentration (4%) of Co ions. Samples were obtained by the pulsed laser deposition (PLD) method with different parameters of the laser ablation. For various samples, the power of laser was changed as well as the temperature of sample heating. Electron paramagnetic resonance (EPR) measurements were carried out and temperature dependence of the EPR spectra was obtained. Analysis of the temperature dependences of the integral intensity of EPR spectra was carried out using the Curie-Weiss law. Fitting yields the following values θCW = 150 K and C = 1.6710, where C is the Curie constant, and θCW is the paramagnetic Curie temperature.

3

Structural, optical, electrical and magnetic properties of sol-gel derived Zn1-x-yCoxAlyO films

Sharma M., Mehra R. M.

Materials Science Poland

|

2008

|

Vol. 26, No. 3

659--673

EN

A detailed study has been presented of optical, electrical, structural and magnetic properties of Zn1.xCoxO (0 < x ≤ 0.25) films co-doped with 1 at. % of Al. The polycrystalline films have been synthesized on Corning glass 7059 substrates by the sol-gel technique using spin coating. Highly preferential c-axis oriented films have been obtained at the annealing temperature of 600 ° C. The lattice constant d of c-axis wurtzite Zn1.x.yCoxAlyO obeys Vegard�fs law for (0 < x ≤ 0.25). The inclusion of Al in ZnO is highly beneficial for the magnetism in ZnO because it enhances the free electron density. Optical spectra measurements reveal that band gap energy exhibits a blue shift upon increasing Co concentration. A positive magnetoresistance for Co doped ZnO and negative magnetoresistance for ZnO without cobalt at 77 K has been observed. The ferromagnetic behaviour has been confirmed by measurements using superconducting quantum interference device. The coercive field and the remanence increase with increase in Co content.