High-temperature ferromagnetic metallic phase in LaMnO3/Sr3Al2O6 heterostructure

Extreme Enhanced Curie Temperature and Perpendicular Exchange Bias in Freestanding Ferromagnetic Superlattices

“…Figure c shows the XRD patterns of STO/(LCMO/SRO) 4 , STO/SAO/(LCMO/SRO) 4 , and freestanding (LCMO/SRO) 4 SLs. Although the peak of SAO is not obvious at the XRD pattern of STO/SAO/(LCMO/SRO) 4 , it can be seen from Figure S2 of the Supporting Information that the out-of-plane lattice parameter of SAO is 16.010 Å, which is close to the value reported in previous literature. , The appearance of higher order strong satellite peaks (denoted as ±1, ±2, ...) around the (002) main peak (described as “0”) in three SLs clearly indicates the formation of the SL structure with periodic modulated components. , The surface morphology shown in Figure S3 of the Supporting Information, with a root square roughness of less than 0.5 nm, can further confirm the good crystalline quality of the sample. The modulation thickness Λ can be calculated from the satellite peak positions using the formula Λ = λ/2­(sin θ i +1 – sin θ i ), , where λ is the wavelength of Cu Kα radiation (0.15407 nm) and θ i and θ i +1 are the angular positions of the i th- and ( i + 1)­th-order satellite peaks, respectively.…”

“…It indicates that the SLs are subjected to in-plane tensile stress, as expected from the lattice mismatch between the STO substrate and upper SLs. STO/SAO/(LCMO/SRO) 4 has a smaller c av as a result of a larger lattice mismatch between the SAO buffer layer and upper SLs …”

“…The exchange integral is proportional to the bond angle of Mn 3+ –O–Mn 4+ . Therefore, the decrease of the modulation thickness can enhance the interfacial tensile strain and bond angle of Mn 3+ –O–Mn 4+ , which is beneficial to strengthen the ferromagnetic double-exchange interaction and T c . ,, In addition, the cationic interdiffusion at the LCMO/SRO interface could occur, which usually can not be avoided in the epitaxy by pulsed laser deposition at high temperatures and can result in the transformation of magnetic properties. For the SRO layer, the decreased temperature of the magnetic ordering is expected via the La, Ca, or Mn doping according to the previous literature. − In the LCMO, the Sr diffusion from SRO can contribute to higher T c , benefiting from the optimized tolerance factor between two neighboring Mn, which was consistent with our observation of enhanced T c at the LCMO/SRO interface.…”

“…Although the peak of SAO is not obvious at the XRD pattern of STO/SAO/ (LCMO/SRO) 4 , it can be seen from Figure S2 of the Supporting Information that the out-of-plane lattice parameter of SAO is 16.010 Å, which is close to the value reported in previous literature. 21,31 The appearance of higher order strong satellite peaks (denoted as ±1, ±2, ...) around the (002) main peak (described as "0") in three SLs clearly indicates the formation of the SL structure with periodic modulated components. 32,33 The surface morphology shown in Figure S3 of the Supporting Information, with a root square roughness of less than 0.5 nm, can further confirm the good crystalline quality of the sample.…”

“…Interfacial effects in the strongly correlated quantum heterostructures have been demonstrated to be an important factor to induce many emergent physical phenomena, mainly as a result of the intricate coupling of multiple degrees of freedom and the delicate balance of competing orders at heterointerfaces. − The strain produced by the substrates, however, still remains to have a significant impact on the ferromagnetic properties in heterostructures or SLs . Thus, by varying the rigid substrate with different strain conditions, one can directly modify the interfacial magnetic couplings, such as interfacial magnetic phase, enhanced magnetic order temperature, and exchange bias. − In other words, the role of the epitaxial strain and interface effects on interfacial magnetic coupling in heterostructures is not yet well-understood and explored.…”