Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

ELECTRICAL AND MAGNETORESISTIVE PROPERTIES OF THE Ag/La_2/3Sr_1/3MnO₃ POINT-PROBE CONTACTS
Irina Černiukė^a, Bonifacas Vengalis^a, Angelė Steikūnienė^a, Gražina Grigaliūnaitė-Vonsevičienė^b, and Antanas Kleopas Oginskis^a
^aCenter for Physical Sciences and Technology, A. Goštauto 11, LT-01108 Vilnius, Lithuania
E-mail: veng@pfi.lt
^bVilnius Gediminas Technical University, Saulėtekio 11, LT-10223 Vilnius, Lithuania

Received 1 October 2014; revised 13 October 2014; accepted 10 December 2014

We report electrical and magnetoresistive properties of Ag point-probe contacts formed by attaching the bent Ag wire (∅ = 0.25 mm) to the top of the La_2/3Sr_1/3MnO₃ (LSMO) thin film magnetron sputtered at 800 °C on MgO(100) single crystal substrates. Significant contact magnetoresistance values (up to 13% at T = 295 K and μ₀H = 0.73 T) have been measured for the Ag/LSMO junctions by applying a 3 point-probe method. The origin of both temperature-dependent resistance and magnetoresistance of the Ag/LSMO contacts has been explained taking into account the dominating role of spreading resistance. It was found that keeping of the films in air for 1 month as well as ultrathin overlayers (d ~ 3–5 nm) of the highly resistive multiferroic BiFeO₃ magnetron sputtered onto the manganite film resulted in a significant increase of contact resistance and reduced magnetoresistance values.

Keywords: manganite films, magnetoresistance, 3 point-probe method, contact resistance, spreading resistance
PACS: 73.40.Cg, 73.43.Qt, 75.47.-m

MAŽO PLOTO Ag/La_2/3Sr_1/3MnO₃ SANDŪRŲ ELEKTRINĖS IR MAGNETOVARŽOS SAVYBĖS

Irina Černiukė^a, Bonifacas Vengalis^a, Angelė Steikūnienė^a, Gražina Grigaliūnaitė-Vonsevičienė^b, Antanas Kleopas Oginskis^a
^aFizinių ir technologijos mokslų centras, Vilnius, Lietuva
^bVilniaus Gedimino technikos universitetas, Vilnius, Lietuva

Darbe tirtos susidariusios mažo ploto Ag/La_2/3Sr_1/3MnO₃ (Ag/LSMO) sandūros elektrinės ir magnetovaržos savybės. Šios sandūros buvo sudaromos mechaniškai prispaudžiant sulenktą Ag vielą (∅ = 0,25 mm) prie plono (LSMO) sluoksnio, užauginto magnetroninio dulkinimo būdu ant kristalinio MgO(100) padėklo, esant 800 °C temperatūrai. Didžiausios tokių sandūrų magnetovaržos vertės, siekiančios 13 % (kai μ₀H = 0,73 T), buvo išmatuotos 295 K temperatūroje naudojant 3-jų elektrodų būdą. Tyrimai parodė, kad darbe tyrinėtų mažo ploto Ag/LSMO sandūrų elektrines ir magnetovaržos savybes lemia po elektrodu esantis ribotas medžiagos tūris, kuriame sutelktos srovės tankio linijos ir jį atitinkanti vadinamoji sutekėjimo elektrinė varža. Papildoma didelės elektrinės varžos paviršinio sluoksnio įtaka buvo parodyta tiriant sandūras, sudarytas ant ilgą laiką ore išlaikytų LSMO sluoksnių paviršiaus, taip pat ant sluoksnio paviršiaus užgarinus ypač ploną (d ~ 3–5 nm) didelės elektrinės varžos BiFeO₃ junginio sluoksnį.

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