Effects of anisotropic strain on perovskite LaMnO3+δ nanoparticles embedded in mesoporous silica

Abstract

We applied anisotropic stress to LaMnO3+δ nanoparticles synthesized in one-dimensional pores of mesoporous silica and investigated the effects of the anisotropic strain on the nanoparticles, which consisted of ferromagnetic and antiferromagnetic particles. The nanoparticles in the one-dimensional pores were crushed without stress in the direction parallel to the silica walls that separated the pores when the mesoporous silica containing the nanoparticles is pressurized. X-ray diffraction patterns of the nanoparticles indicated that the lattice strain increased with increasing applied pressure. The lattice constants were found to reduce anisotropically, and the values saturated above a critical strain. Both the ferromagnetic and antiferromagnetic transition temperatures for the LaMnO3+δ nanoparticles initially increased with increasing pressure and then remained constant at around the critical strain. These results indicate that anisotropic stress causes distortion of the shape of nanoparticles. This induces an increase in the lattice strain and the anisotropic compression of the crystal structure, which, in turn, results in an increase in the transition temperatures.

Pressure effects in hollow and solid iron oxide nanoparticles

“…In the case of nanoparticles (NPs), pressure modifies the transition temperature [1], the susceptibility and magnetization [2,3], the hysteresis cycles [2] and the effective anisotropy energy barrier [4]. The effect of pressure in the NPs core and surface is distinct, allowing disentanglement of core and shell magnetic properties.…”

Crystalline Mesoporous Complex Oxides: Porosity‐Controlled Electromagnetic Response

“…[ 23–30 ] The magnetic ordering temperature (Curie temperature or Néel temperature) in magnetic materials is highly size‐, strain‐, and surface‐sensitive. [ 25,29,31–36 ] Many magnetic nanostructures exhibit unusual low‐temperature magnetic properties. [ 37,38 ] Nanoporous ferrite materials have also been reported to show altered magnetic ordering.…”

Strain controlled orbital state and magnetization in insulating LaMnO3+δ films

“…From the center of the reciprocal lattice node of the LaMnO 3þd film, the in-plane and out-of-plane parameters are calculated to be 3.899 Å and 3.904 Å , respectively. Based on the previous studies, 12,22 the lattice parameters of the LaMnO 3þd single crystal vary with d. a parameters is 3.903 Å and 3.894 Å for LaMnO 3.09 and LaMnO 3.125 , respectively. Therefore, our LaMnO 3þd film has an excess oxygen d $ 0.1.…”

“…The FC data show FM behavior, while ZFC one shows blocking transition in all films, indicating the FM property comes from the FM nanoclusters. 22 The negative magnetization during ZFC cycle measured in low applied field may originate from an intrinsic effect from uncompensated spins or an artifact due to the diamagnetic signal from the background. These results are consistent with those in LaMnO 3þd films, 25 (LaMnO 3 ) N /(SrTiO 3 ) N superlattices 26 and La 0.66 Sr 0.63 MnO 3 -contained nanostructure.…”

“…20,21 In LaMnO 3þd films, the enhancement of insulator-to-metal transition temperature T P was reported with decreasing the tensile strain. 22 Seldom attention is focused on the strain effect, especially compressive strain, on the magnetic properties of insulating LaMnO 3þd films. In the present work, LaMnO 3þd films with various thicknesses are prepared under the same amount of oxygen atmosphere on LaAlO 3 substrate.…”