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Strain engineering induced interfacial self-assembly and intrinsic exchange bias in a manganite perovskite film.

Cui B, Song C, Wang GY, Mao HJ, Zeng F, Pan F - Sci Rep (2013)

Bottom Line: The control of complex oxide heterostructures at atomic level generates a rich spectrum of exotic properties and unexpected states at the interface between two separately prepared materials.The frustration of magnetization and conductivity of manganite perovskite at surface/interface which is inimical to their device applications, could also flourish in tailored functionalities in return.The present results not only provide a strategy for producing a new class of delicately functional interface by strain engineering, but also shed promising light on fabricating the EB part of spintronic devices in a single step.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.

ABSTRACT
The control of complex oxide heterostructures at atomic level generates a rich spectrum of exotic properties and unexpected states at the interface between two separately prepared materials. The frustration of magnetization and conductivity of manganite perovskite at surface/interface which is inimical to their device applications, could also flourish in tailored functionalities in return. Here we prove that the exchange bias (EB) effect can unexpectedly emerge in a (La,Sr)MnO3 (LSMO) "single" film when large compressive stress imposed through a lattice mismatched substrate. The intrinsic EB behavior is directly demonstrated to be originating from the exchange coupling between ferromagnetic LSMO and an unprecedented LaSrMnO4-based spin glass, formed under a large interfacial strain and subsequent self-assembly. The present results not only provide a strategy for producing a new class of delicately functional interface by strain engineering, but also shed promising light on fabricating the EB part of spintronic devices in a single step.

No MeSH data available.


Related in: MedlinePlus

Magnetic and electric properties for LSMO samples with various thicknesses.(a), Normalized M-H curves measured at 5 K after field cooling from room temperature in 20 kOe. M-T and R-T curves for different LSMO thicknesses (7, 30, 45, 60, and 150 u.c.) are presented in (b) and (c), respectively. For clarity, the moment in M-T curves are multiplied by a coefficient as shown.
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f4: Magnetic and electric properties for LSMO samples with various thicknesses.(a), Normalized M-H curves measured at 5 K after field cooling from room temperature in 20 kOe. M-T and R-T curves for different LSMO thicknesses (7, 30, 45, 60, and 150 u.c.) are presented in (b) and (c), respectively. For clarity, the moment in M-T curves are multiplied by a coefficient as shown.

Mentions: Measurements performed over a range of LSMO thicknesses offer further insight into the EB effect and growth dynamics of self-assembled structures. A series of LSMO with different thicknesses on LSAO were then prepared. The EB behavior as a function of LSMO thickness is shown in Fig. 4a and its inset. The increase of film thickness to 45 u.c. boosts the HEB to the maximum of 246 Oe, and then HEB is reduced to 30 Oe for 150 u.c as expected, ascribed to the thick FM layer in the EB system29. Particularly, there is no resolvable exchange bias in fully strained 7 u.c. LSMO, indicating the absence of AFM phase in such ultrathin films. We confirm this speculation by a HAADF-STEM image and corresponding EDX results (Supplementary Fig. S7). Explanations may include that there is no lattice relaxation and space for phase separation in ultrathin films with several monolayers. At the initial growth stage (7 u.c.), the lattice volume of LSMO (53.4 Å3) is much smaller than that of its bulk (57.9 Å3), indicating the existence of a large compressive strain (Supplementary Fig. S8). Consequently, both the magnetism and conductivity are seriously suppressed, leading to a nonmetallic and weak-ferromagnetic LSMO with a low Curie temperature (TC) of ~122 K, as shown in Fig. 4b and c. When the LSMO thickness increases, the lattice volume approaches to the value of the bulk, causing the monotonous enhancement of both TC and conductivity. The 45 u.c. LSMO sample shows a transition from a nonmetallic to metallic state considering the tendency of the temperature dependent resistivity. Nevertheless the thick samples, e.g., 150 u.c., show a much lower resistivity with a typical metallic state and TC ≈ 310 K.


Strain engineering induced interfacial self-assembly and intrinsic exchange bias in a manganite perovskite film.

Cui B, Song C, Wang GY, Mao HJ, Zeng F, Pan F - Sci Rep (2013)

Magnetic and electric properties for LSMO samples with various thicknesses.(a), Normalized M-H curves measured at 5 K after field cooling from room temperature in 20 kOe. M-T and R-T curves for different LSMO thicknesses (7, 30, 45, 60, and 150 u.c.) are presented in (b) and (c), respectively. For clarity, the moment in M-T curves are multiplied by a coefficient as shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3756339&req=5

f4: Magnetic and electric properties for LSMO samples with various thicknesses.(a), Normalized M-H curves measured at 5 K after field cooling from room temperature in 20 kOe. M-T and R-T curves for different LSMO thicknesses (7, 30, 45, 60, and 150 u.c.) are presented in (b) and (c), respectively. For clarity, the moment in M-T curves are multiplied by a coefficient as shown.
Mentions: Measurements performed over a range of LSMO thicknesses offer further insight into the EB effect and growth dynamics of self-assembled structures. A series of LSMO with different thicknesses on LSAO were then prepared. The EB behavior as a function of LSMO thickness is shown in Fig. 4a and its inset. The increase of film thickness to 45 u.c. boosts the HEB to the maximum of 246 Oe, and then HEB is reduced to 30 Oe for 150 u.c as expected, ascribed to the thick FM layer in the EB system29. Particularly, there is no resolvable exchange bias in fully strained 7 u.c. LSMO, indicating the absence of AFM phase in such ultrathin films. We confirm this speculation by a HAADF-STEM image and corresponding EDX results (Supplementary Fig. S7). Explanations may include that there is no lattice relaxation and space for phase separation in ultrathin films with several monolayers. At the initial growth stage (7 u.c.), the lattice volume of LSMO (53.4 Å3) is much smaller than that of its bulk (57.9 Å3), indicating the existence of a large compressive strain (Supplementary Fig. S8). Consequently, both the magnetism and conductivity are seriously suppressed, leading to a nonmetallic and weak-ferromagnetic LSMO with a low Curie temperature (TC) of ~122 K, as shown in Fig. 4b and c. When the LSMO thickness increases, the lattice volume approaches to the value of the bulk, causing the monotonous enhancement of both TC and conductivity. The 45 u.c. LSMO sample shows a transition from a nonmetallic to metallic state considering the tendency of the temperature dependent resistivity. Nevertheless the thick samples, e.g., 150 u.c., show a much lower resistivity with a typical metallic state and TC ≈ 310 K.

Bottom Line: The control of complex oxide heterostructures at atomic level generates a rich spectrum of exotic properties and unexpected states at the interface between two separately prepared materials.The frustration of magnetization and conductivity of manganite perovskite at surface/interface which is inimical to their device applications, could also flourish in tailored functionalities in return.The present results not only provide a strategy for producing a new class of delicately functional interface by strain engineering, but also shed promising light on fabricating the EB part of spintronic devices in a single step.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.

ABSTRACT
The control of complex oxide heterostructures at atomic level generates a rich spectrum of exotic properties and unexpected states at the interface between two separately prepared materials. The frustration of magnetization and conductivity of manganite perovskite at surface/interface which is inimical to their device applications, could also flourish in tailored functionalities in return. Here we prove that the exchange bias (EB) effect can unexpectedly emerge in a (La,Sr)MnO3 (LSMO) "single" film when large compressive stress imposed through a lattice mismatched substrate. The intrinsic EB behavior is directly demonstrated to be originating from the exchange coupling between ferromagnetic LSMO and an unprecedented LaSrMnO4-based spin glass, formed under a large interfacial strain and subsequent self-assembly. The present results not only provide a strategy for producing a new class of delicately functional interface by strain engineering, but also shed promising light on fabricating the EB part of spintronic devices in a single step.

No MeSH data available.


Related in: MedlinePlus