Objectives


Project aims the theoretical study of new types of magnetic junctions tunnel barriers on alkaline halides or alkaline-earth system having large magnetoresistance.

NEWS


Funded by





INNOVATION AND CREATIVITY

EXECUTIVE UNIT FOR FINANCING EDUCATION HIGHER, RESEARCH AND DEVELOPMENT AND INNOVATION



"Alkali and silver halides based magnetic tunnel junctions"
Project Registration Code: PN-II-ID-PCE-2012-4-0028
            Number of contract.45/02.09.2013
Executive report for 2016!
(in english)
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EXECUTIVE REPORTS AND RESULTS
2016

The electronic, magnetic and transport properties of Fe/NaBr/Fe(001), Fe/AgBr(LiBr)/Fe(001) and Fe/LiF/Fe(001) heterojunctions were investigated. Two model interfaces were considered with Fe atoms situated atop of Na and Br positions (C1) and in the hollow between Na and Br sites (C2), respectively. A highly magnetoresistive effect was shown, in case of C1 type interface, of   104 %. The transport properties of the heterojunctions having Ag1-xNax barrier were also analysed. The crystal structures, magnetic and transport properties of Ca2(Fe,Ni)MoO6 perovskites were investigated. The distributions of iron and molybdenum ions in B and B` sites as well as their valence states, have been analysed in correlation with their physical properties. A new model is proposed in order to describe the magnetic properties of heavy rare-earth RCo2 compounds.

Papers published in the framework of the grant in ISI quoted journals or presented at International Conferences

Executive report for 2016! (in english)

Papers

  1. "Are insulating LiF barriers relevant for spin-polarized tunneling applications? Insights from first principles calculations", P. Vlaic, E.Burzo, K. Carva, J. Phys.D: Appl. Phys. 49, 305302 (2016)
  2. "Spin-polarized transport using do ferromagnetism: an ab initio study of CaC/MgS/CaC(001) heterojunctions", P. Vlaic, E. Burzo, K. Carva, J. Phys. D.: Appl. Phys. 48, 455002 (2015)
  3. "Magnetic and electronic transport properties of some tunnel junctions with AgBr spin filter barrier", P.Vlaic, E.Burzo, J. Phys.: Cond. Matter, (accepted to be published)
  4. "Structural and magnetic properties of Ca1.5La0.5FeMoO6 perovskites at high pressures", E.Burzo, D.P.Kozlenko, N.T.Dang, S.E.Kichanov, N.O.Golosova, Journal of Alloys and Compounds 664, 363 (2016)
  5. "Crystal structures, magnetic and transport properties of calcium based perovskites", E.Burzo, I.Balasz, AIP Conf. Proc. 1722, 080003 (2016)
  6. "Ferrimagnetic order in Ca2(Fe,Ni)MoO6 perovskites", E.Burzo, I.Balasz,  Rom. J. Phys. (2017) (accepted to be published)

Paper published in addition to the main topics

  1. "Magnetic and magnetocaloric properties of Er1-xYxCo2 compounds with x ≤ 0.3", E.Burzo, I.Balasz, L. Chioncel, Rom. Journ. Phys., Vol. 61, No. 7–8, P. 1213–1223 (2016)
  2. "Exchange interactions in heavy rare-earth RCo2 compounds", E.Burzo, J.Phys.: Conf. Series (accepted to be published)


Conferences



2015

The ground state electronic, magnetic and spin dependent transport properties of Fe/LiF(LiBr)/Fe(001) tunnel junctions were studied. The interfaces stability has been analysed in correlations with interdiffusion effects. Iron induced states (MIGs) are evidenced at barriers interfaces. The k||-resolved conductances are well described by the tunneling mechanism across the barriers. Additional data were obtained on CaC/MgS/CaC(001) tunnel junctions. The current spin-polarization reaches values as high as 99%, the magnetoresistive ratios being of the order of 104 %. The structural, magnetic and transport properties of Ca2Fe1-xNixMoO6 perovskites were studied. Magnetoresistive ratios up to 36% were obtained at T=10K. Changes in valence states of transition metal ions, as effect of pressure in (Ca,La)FeMoO6 perovskites, were correlated with the evolution of structure parameters.

Executive report for 2015! (in english)

Papers

  1. "Oscillatory exchnage coupling and strong direct tunneling in AgCl based heterojunctions", P.Vlaic, E.Burzo, K.Carva J.Alloys Comp. 630, 299-309 (2015)
  2. "Spin-polarized transport using do ferromagnetism: and ab initio study of CaC/MgS/CaC(001) heterojunctions", P.Vlaic, E.Burzo, K.Carva, J. Phys. D.: Appl. Phys. 48, 455002-455010 (2015)
  3. "Magnetic and trasport properties of Ca1.5La0.5FeMo1-xWxO6 perovskites", E.Burzo, I.Balasz, M.Valeanu, D.P.Kozlenko, G.E.Kichanov, A.V.Rutkauskas, B.N.Savenko, Journal of Alloys and Compounds 621, 71-77 (2015)
  4. "Pressure effects on the magnetic behaviour of cobalt in rare-earth compounds", E.Burzo, P.Vlaic, D.P.Kozlenko, Rom. J. Phys. 60, 200 (2015)
  5. "Crystal structures, magnetic and transport properties of calcium based perovskites", E.Burzo, I.Balasz, AIP Conf. Proc. (in press)
  6. "Structural and magnetic properties of Ca1,5La0,5FeMoO6 perovskite at high pressure", E.Burzo, D.P.Kozlenko, N.T.Dang, S.E.Kichanov, N.O.Galosova, Journal of Alloys and Compounds (Available online 4 January 2016)
  7. "Are insulating LiF barriers relevant for spin-polarized tunneling applications? Insight from first-principles", E.Burzo, P.Vlaic, K.Carva, Journal Phys.D:Appl. Phys. (sent for publication)


Conferences


Paper published in addition to the main topics

"Sequential cobalt magnetization collapse in ErCo2: beyond the limits of itinerant electron metamagnetism", D.P.Kozlenko, E.Burzo, P.Vlaic, S.E.Koichanov, A.V.Rutkauskas, B.N.Savenko, Scientific Reports (UK) 5, 8620 (2015)

2014

The structural, electronic and spin-dependent transport properties of Fe/AgCl/Fe (001) and CaC/X/CaC (001) with X = LiCl and MgS magnetic junctions were studied. High magnetoresistance ratios are predicted. The interdiffusion of Ag at the Fe/AgCl interfaces has been analysed. The effects of W substitution on (Ca, La, Fe, Mo)O6 double perovskites were studied. The spin polarization increases as the crystallographic ordering is higher as result of Mo substitution by W. The physical properties of some R-Fe(Co) compounds, of technical interest are analysed.

Executive report for 2014! (in english)

Papers

  1. ”Impact of Fe/NaCl(001) interface structure on electronic, magnetic and spin-polarized transport properties Fe/NaCl/Fe(001) heterojunctions: an ab initio study”, P. Vlaic, E.Burzo and K.Carva, J. Alloys Comp. 598, 41 (2014)
  2. "Magnetic and Transport Properties of Ca1.5La0.5FeMo1-xWxO6 Perovskites", E. Burzo, I. Balasz, M. Valeanu, D.P.Kozlenko, S.E. Kichanov, A.V. Rutkauskas, B.N. Savenko, J. Alloys Comp. 621, 71 (2015)
  3. “Pressure effects on the magnetic behavior of cobalt in rare-earth compounds”, E. Burzo, P. Valic, D.P. Kozlenko, Rom. J. Phys. 60, 1 (2015)
  4. "Oscillatory exchange coupling and strong direct tunneling in AgCl based heterojunctions", P.Vlaic, E.Burzo, K.Carva, Journal of Alloys and Compounds (Available online 16 January 2015)
  5. "Electronic structure and spin polarized transport characteristics of CaC/LiCl(MgS)/CaC(001) heterojunctions", P.Vlaic, E.Burzo, AIP Conference Proceeding (in press)
  6. "Exchange enhanced paramagnetism of rare-earth (yttrium)- transition metal compounds", E.Burzo, AIP Conf. Proc. 1694, 030001 (2015)


Conferences



2013

Structural, electronic and spin-dependent transport properties of  Fe/NaCl/Fe(001) and Fe/CaS/Fe(001) tunnel junctions were studied by means of first-principle calculation. Resonant tunneling has been shown to play a major role on the spin-polarized transport properties. High magnetoresistance ratios in Fe/NaCl/Fe junctions, comparable to those evidenced in Fe/MgO/Fe ones are predicted. No interfacial interdiffusion between Fe and NaCl layers has been shown. A small exchange coupling with the sign depending on the Fe/CaS(001) interface structure and strength decaying exponentially with the barrier has been evidenced. The main contribution to the current in the ferromagnetic state of the junction is given by the minority-spin electrons. The pressure effects on the physical properties of RCo5 compounds were also studied.

Executive report for 2013! (in english)

Papers

  1. "Structural, electronic, magnetic and spin dependent transport properties of Fe/CaS/Fe (001) heterostructures", P. Vlaic, E. Burzo and K. Carva, J. Appl. Phys. 113, 053715 (2013)
  2. ”Pressure effects on crystal structures and magnetic properties of RCo5 (R = Y or Gd) compounds”, E.Burzo, P. Vlaic, AIP Conf. Proc. 1564, 96 (2013)

Conferences


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