Optimized procedure for sol–gel production of La Ca MnO ... · Optimized procedure for sol–gel...
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ORIGINAL PAPER Optimized procedure for sol–gel production of La 2/3 Ca 1/3 MnO 3 thin films Keller Andrews 1 • Anthony B. Kaye 1 Received: 1 June 2015 / Accepted: 25 June 2015 Ó Springer Science+Business Media New York 2015 Abstract Lanthanum calcium manganese oxide La ð1xÞ Ca x MnO 3 Þ has a number of potentially useful magnetic and electrical properties that can be adjusted based upon its calcium fraction, x. This material has been fabricated in a number of ways, but as we approach a point at which it can be used in complex commercial applications, it is critical that we consider the cost of generating thin films in complex geometries. Therefore, we present an optimized sol–gel synthesis and thin-film generation procedure that results in repeatable, high-quality thin films of a specified thickness. Graphical Abstract Keywords Magnetic oxides Sol–gel processing Thin- film structure and morphology 1 Introduction A number of materials with a perovskite crystalline struc- ture exhibit solid–solid phase transitions that also have interesting and potentially useful magnetic properties [1]. The perovskites lanthanum manganese oxide ðLaMnO 3 Þ and calcium manganese oxide ðCaMnO 3 Þ have each been studied for their individual magnetic properties for more than 60 years [2]. When the two are combined, however, they form a modified perovskite structure that takes advantage of the ‘‘flexibility’’ of manganese that exists in both trivalent and tetravalent forms. By doping one man- ganese oxide with the other, we observe an enhancement of some of the previously observed magnetic effects. As one example, by heavily doping LaMnO 3 with divalent calcium atoms, the resulting material has significantly enhanced colossal magnetoresistance (up to 127,000 % [3]), far beyond that of undoped LaMnO 3 [4]. Because of these enhanced effects, the doped compound, lanthanum calcium manganese oxide (La 1x Ca x MnO 3 ; hereafter, LCMO), has become more widely studied than either of its constituents (see, e.g., [5] and references therein). Although the fraction of possible Ca doping ranges from x ¼ 0 (pure LaMnO 3 ) to x ¼ 1 (pure CaMnO 3 ), our prin- cipal interest in LCMO is the phase transition between the ferromagnetic metallic state to the paramagnetic insulating state, which occurs at calcium dopant levels (x) in the range 0:2\x\0:4 (see, e.g., [6] and [7]). In order to take advantage of the highest insulator-to-metal transition temperature T IMT ð Þ possible for the ultrafast solid–solid phase transition, the most common single calcium dopant Keller Andrews and Anthony B. Kaye have contributed equally to this work. & Keller Andrews [email protected] Anthony B. Kaye [email protected] 1 Department of Physics and the Nano Tech Center, Texas Tech University, Lubbock, Texas 79409, USA 123 J Sol-Gel Sci Technol DOI 10.1007/s10971-015-3785-2
Transcript of Optimized procedure for sol–gel production of La Ca MnO ... · Optimized procedure for sol–gel...
ORIGINAL PAPER
Optimized procedure for sol–gel production of La2/3Ca1/3MnO3
thin films
Keller Andrews1 • Anthony B. Kaye1
Received: 1 June 2015 / Accepted: 25 June 2015! Springer Science+Business Media New York 2015
Abstract Lanthanum calcium manganese oxide Lað1"xÞ!
CaxMnO3Þ has a number of potentially useful magnetic and
electrical properties that can be adjusted based upon its
calcium fraction, x. This material has been fabricated in anumber of ways, but as we approach a point at which it can
be used in complex commercial applications, it is criticalthat we consider the cost of generating thin films in complex
geometries. Therefore, we present an optimized sol–gel
synthesis and thin-film generation procedure that results inrepeatable, high-quality thin films of a specified thickness.
Graphical Abstract
Keywords Magnetic oxides $ Sol–gel processing $ Thin-film structure and morphology
1 Introduction
A number of materials with a perovskite crystalline struc-ture exhibit solid–solid phase transitions that also have
interesting and potentially useful magnetic properties [1].
The perovskites lanthanum manganese oxide ðLaMnO3Þand calcium manganese oxide ðCaMnO3Þ have each been
studied for their individual magnetic properties for more
than 60 years [2]. When the two are combined, however,they form a modified perovskite structure that takes
advantage of the ‘‘flexibility’’ of manganese that exists in
both trivalent and tetravalent forms. By doping one man-ganese oxide with the other, we observe an enhancement of
some of the previously observed magnetic effects. As one
example, by heavily doping LaMnO3 with divalent calciumatoms, the resulting material has significantly enhanced
colossal magnetoresistance (up to 127,000 % [3]), far
beyond that of undoped LaMnO3 [4]. Because of theseenhanced effects, the doped compound, lanthanum calcium
manganese oxide (La1"xCaxMnO3; hereafter, LCMO), hasbecome more widely studied than either of its constituents
(see, e.g., [5] and references therein).
Although the fraction of possible Ca doping ranges fromx ¼ 0 (pure LaMnO3) to x ¼ 1 (pure CaMnO3), our prin-
cipal interest in LCMO is the phase transition between the
ferromagnetic metallic state to the paramagnetic insulatingstate, which occurs at calcium dopant levels (x) in the range
0:2\x\0:4 (see, e.g., [6] and [7]). In order to take
advantage of the highest insulator-to-metal transitiontemperature TIMTð Þ possible for the ultrafast solid–solid
phase transition, the most common single calcium dopant
Keller Andrews and Anthony B. Kaye have contributed equally to thiswork.
& Keller [email protected]
Anthony B. [email protected]
1 Department of Physics and the Nano Tech Center, TexasTech University, Lubbock, Texas 79409, USA
123
J Sol-Gel Sci Technol
DOI 10.1007/s10971-015-3785-2
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