Alexandru Cel Bun College

Gura Humorului, Romania

Alexandru Cel Bun College

Gura Humorului, Romania
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Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Pinzaru D.,Al. I. Cuza University | Pascariu P.,Al. I. Cuza University | And 3 more authors.
Materials Chemistry and Physics | Year: 2011

A series of Co, Ni and Co-Ni granular thin films with variable nitrogen content in the range 0-16 at.% N were prepared by electrodeposition onto aluminum substrate. The nitrogen content was varied in order to analyze its influence on the magnetoresistance. The morphology, structure and magnetic properties of electrodeposited Co, Ni and Co-Ni granular thin films were also studied as a function of the nitrogen content. The magnetoresistance (MR) ratio of Co-Ni-N granular films initially increased and then decreased when increasing the nitrogen content. The films exhibit a granular morphology, with rich in nitrogen frontiers between grains and some un-deposited sites on the aluminum substrate, which easily oxidize even during the process of preparation, favoring the spin tunneling transport. We obtained tunneling magnetoresistance (TMR) effect in the Co-Ni-N granular thin films in the range 3-159%; this large effect obtained in Co-Ni-N granular thin films makes them suitable for applications in electronics. © 2011 Elsevier B.V. All rights reserved.


Pinzaru D.,Al. I. Cuza University | Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Pascariu P.,Al. I. Cuza University | And 3 more authors.
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2011

We report in this paper the first observation of giant magnetoresistance as high as 23% in electrodeposited [Fe/Pt]n granular multilayers with different thicknesses of bi-layers. [Fe/Pt]n multilayers were prepared by electrodeposition, through the single bath technique. Cu (100) textured polycrystalline foils were used as substrate. The composition of the studied samples is Cu:Pt(x nm)/[Fe(tFe nm)/Pt(x nm)]n, in which the thickness of the iron layer varied between 2.5÷12.5 nm while the thickness of the non-magnetic Pt layer is varied by changing the bottom Pt layer thickness x between 0.5÷3.0 nm. The SEM characterization of the multilayer revealed a granular structure of the deposit with the granule diameter in the range from 2 to 11 nm. These results are comparable with those obtained by the X-ray diffraction measurements of crystallites size obtained by the Scherer equation. The hysteresis loops showed that the magnetic properties are influenced both by the thickness of the bi-layer and by the number of periods (n). The coercivity (Hc) varied in the range 8÷21 kA-1 and the remanence ratio was M/Ms = 0.23÷0.81. The samples display out of plane anisotropy and anti-ferromagnetic type coupling between layers, as it was emphasized by means of the torsion magnetometer. [Fe/Pt]n electrodeposited multilayers display giant magnetoresistance effect which can be explained mainly by the exchange interaction among neighbouring layers and by the spatially inhomogeneous magnetic structure of the granular multilayer (favouring spin scattering at the interfaces between grains and layers).


Tanase S.I.,Stefan Cel Mare University of Suceava | Tanase S.I.,Alexandru Cel Bun College | Tanase D.,Stefan Cel Mare University of Suceava | Dobromir M.,Al. I. Cuza University | And 2 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2016

The effect was investigated of nitrogen impurities on the morphology and magnetoresistance properties of Co–N and Ni–N thin films. The films were electroplated onto aluminum substrates, at room temperature, using the same electrodeposition parameters (pH = 3 and temperature 30 ∘C) for all experiments. The films were compared with similar samples obtained in the absences of nitrogen impurities. Scanning electron microscopy, X-ray photoelectron spectroscopy, and magnetoresistance measurements were utilized to characterize the studied films. The presence of nitrogen in the electrodeposited films have a significant influence on the morphology and magnetoresistance of electrodeposited films. Incorporation of a small amount of nitrogen into electrodeposited films increases the magnetoresistance up to 0.21 % for Co–N thin films and respectively 0.65 % in the case of Ni–N films. We suppose that the shape of the magnetoresistance curves is influenced by the interaction between the magnetic moment of the neighboring Co or Ni grains (with ferromagnetic behavior) separated by the nonmagnetic regions. Interfacial complexities of a ferromagnetic metal/oxide interface in studied thin films could force the interfacial spins to align ferromagnetically or antiferromagnetically. They could be useful for technological applications in electronics. © 2015, Springer Science+Business Media New York.


Pascariu P.,Al. I. Cuza University | Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Tanase D.P.,Al. I. Cuza University | And 2 more authors.
Materials Chemistry and Physics | Year: 2012

In this report we describe some experimental results concerning the preparation by electrodeposition and characterization of Co/Zn multilayer films, a system of special significance because Co and Zn are immiscible in a large range of compositions, permitting an easier adaptation of the sharp interfaces and the magnetic interactions between layers, with a view to obtain technological applications in nano-electronics. We established the working parameters for electrodeposition of multilayer films based on Co and Zn nanoscale layers, using a dual-bath potentiostatic electrodeposition method. The effect of the first electrodeposited layer growth process on the structure and magnetic properties of the multilayer were studied by using two series of multilayers of varying periods, starting with Co or Zn layers, respectively (with the same total thickness of Co layers, namely 50 layers of 5 nm thick, but various Zn layer thickness). These properties were also studied as a function of the Zn layer thicknesses (varying between 0.1 nm and 5.9 nm), for the two series of films. The magnetoresistance (in the current in plane configuration with dc magnetic field applied in the film plane), varied with Zn layer thickness, exhibiting a giant magnetoresistance contribution of about 30% in the case of [Co (5 nm)/Zn (2.7 nm)] 50 films. © 2011 Elsevier B.V. All rights reserved.


Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Stefan Cel Mare University of Suceava | Tanase S.I.,Alexandru Cel Bun College | Tanase D.,Al. I. Cuza University | And 3 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2012

The surface morphology and magnetic properties of Co-Ni-N thin films electrodeposited under an external magnetic field were investigated. The films were electroplated on Al substrates using the same electrodeposition parameters (temperature and pH) for all experiments, with an external magnetic field of 107 Oe applied to the cathode surface. The films were compared with similar samples obtained in the absences of magnetic field. The magnetoinduced modifications in the Co-Ni-N morphology can be explained by the specific local convection of ions at the interface cathode-electrolyte, which promotes changes both in the electrical charge of the double layer and in the thickness of the diffusion layer. From the magnetic measurements, we found that the coercivity varied between Hc = (14 ÷ 27) kA/m depending on the direction of the applied magnetic field and on the sodium nitrate content in the plating bath. It was observed that an induced anisotropy ap- peared in the Co-Ni-N films due to the preferential orientation of the easy axis of magnetization in the magnetic field direction. In addition, the Co-Ni-N alloy films showed good magnetic property, which is considered that not only the smaller grain size of the films, but also more uniform surface of the films than that deposited in absence of applied magnetic field. © Springer Science+Business Media, LLC 2012.


Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Tanase D.P.,Al. I. Cuza University | Dobromir M.,Al. I. Cuza University | Georgescu V.,Al. I. Cuza University
Applied Surface Science | Year: 2011

We present in this paper several results concerning the preparation by means of electrolysis and characterization of Co-Ni-Mo thin films. Co-Ni-Mo thin films with different molybdenum content in the range 0-25 at% Mo were prepared from a complex solution containing ions of Co, Ni and Mo, using galvanostatic control, on aluminum substrates. The effects of applied current density on the morphology, magnetic, magnetoresistance, and optical properties of the electrodeposited Co-Ni-Mo films were investigated. The applied current density significantly influenced the film composition and their magnetic properties. The increase of molybdenum content in Co-Ni films (up to 25 at% Mo) enhances the resistivity, but it reduces the magnetoresistance effect. We report the first observation of magnetoresistance as high as 8% in Co-Ni-Mo thin films. © 2011 Elsevier B.V. All rights reserved.


Pascariu P.,Al. I. Cuza University | Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Pinzaru D.,Al. I. Cuza University | Georgescu V.,Al. I. Cuza University
Journal of Superconductivity and Novel Magnetism | Year: 2011

In this work, we report experimental results concerning the giant magnetoresistance effect and the magnetic properties of [Co/Zn] n and [Zn/Co] n electrodeposited multilayers. Two series of multilayers starting with Co and Zn layers, respectively, were grown onto Cu (100) substrate under identical conditions. We investigated the effect of the seed layer (Co or Zn) and Zn layer's thicknesses on the magnetic and magnetoresistant properties of electrodeposited multilayers. We found out that the magnetic anisotropy and the shape of the hysteresis cycle are strongly influenced by the multilayer features. The magnetic properties of the [Co/Zn] n and [Zn/Co] n strongly depend on the Zn thickness and on the seed layer (the first layer deposited onto the Cu substrate). The coercivity fields varied between (145 Oe-208 Oe) as a function of the Zn layer's thicknesses. [Co/Zn] n and [Zn/Co] n electrodeposited multilayers display magnetoresistance (14%) effect which can be explained mainly by the exchange interaction among neighboring layers and by the spatially inhomogeneous magnetic structure of the nanostructured multilayer; in addition, the thickness of the Zn interlayer has an important role on the transportation and diffusion processes. © 2011 Springer Science+Business Media, LLC.


Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Pinzaru D.,Al. I. Cuza University | Georgescu V.,Al. I. Cuza University
Journal of Superconductivity and Novel Magnetism | Year: 2011

The effect of nitrogen addition on the morphology, magnetic anisotropy, and magnetoresistance properties of Co-Ni-N granular thin films were investigated. The films were grown by electrodeposition onto aluminum substrates at room temperature. By a complex process of cationic catalysis occurring at the cathode/electrolyte interface, nitrogen is adsorbed in the Co-Ni film. Finally, a granular film grows by a tridimensional progressive nucleation mechanism. The nature of the grains and of the interface between them influences exchange interactions between grains, which play an important role in determining the magnetic anisotropy. From the magnetic measurements, we found that the magnetic anisotropy constant varied in the range K eff=(-21.5÷36.6) ×10 4 J·m -3 and the coercivity varied between H c=(13÷67) kA·m -1 depending on the sodium nitrate content in the plating bath. The Co-Ni-N granular thin films display large values (∼160%) of magnetoresistance. These large values of magnetoresistance make such structures attractive for applications as sensitive magnetic field sensors. © 2011 Springer Science+Business Media, LLC.


Pinzaru D.,Al. I. Cuza University | Tanase S.I.,Al. I. Cuza University | Tanase S.I.,Alexandru Cel Bun College | Pascariu P.,Al. I. Cuza University | And 3 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2011

In this paper, we report experimental results concerning the magnetic properties and the magnetoresistance effect of [Fe/Pt] n and [Pt/Fe] n electrodeposited multilayers. Two series of multilayers starting with Pt and Fe layers, respectively, were grown onto glass substrate covered with electroless deposited amorphous Ni. We investigated the effect of the seed layer (Pt or Fe) and Pt layer thicknesses on the magnetic and magnetoresistance properties of electrodeposited multilayers. The structure and morphology of the samples were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The hysteresis loops of the [Fe/Pt] n and [Pt/Fe] n multilayers showed that the magnetic properties strongly depend on the Pt thickness and on the seed layer (the first layer deposited onto the glass substrate). [Fe/Pt] n and [Pt/Fe] n electrodeposited multilayers display magnetoresistance (∼15%) effect which can be explained mainly by the spin-dependent scattering of conduction electrons between Fe layers through a Pt layer and by the existence of anti-ferromagnetic coupling between subsequent Fe layers. The existence of a GMR effect in Fe/Pt multilayers is very promising for technological applications (e.g., magnetoresistance sensors). © 2011 Springer Science+Business Media, LLC.

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