We investigate the influence of a well-defined reversible biaxial strain $\ensuremath{\leqslant}0.12%$ on the magnetization $(M)$ of epitaxial ferromagnetic manganite films. $M$ has been recorded depending on temperature, strain and magnetic field in $20--50\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thick films. This is accomplished by reversibly compressing the isotropic in-plane lattice parameter of the rhombohedral piezoelectric 0.72PMN-0.28PT (001) substrates by application of an electric field $E\ensuremath{\leqslant}12\phantom{\rule{0.3em}{0ex}}\mathrm{kV}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. The magnitude of the total variable in-plane strain has been derived. Strain-induced shifts of the ferromagnetic Curie temperature $({T}_{C})$ of up to $19\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ were found in ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ (LSMO) and ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ films and are quantitatively analyzed for LSMO within a cubic model. The effective magnetoelectric coupling coefficient $\ensuremath{\alpha}={\ensuremath{\mu}}_{0}dM∕dE\ensuremath{\leqslant}6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\phantom{\rule{0.3em}{0ex}}\mathrm{s}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}$ at ambient temperature in the magnetic-film-ferroelectric-substrate system results from the strain-induced $M$ change. It corresponds to an enhancement of ${\ensuremath{\mu}}_{0}\ensuremath{\Delta}M\ensuremath{\leqslant}19\phantom{\rule{0.3em}{0ex}}\mathrm{mT}$ upon biaxial compression of 0.1%. The extraordinary large $\ensuremath{\alpha}$ originates from the combination of three crucial properties: (i) the strong strain dependence of $M$ in the ferromagnetic manganites, (ii) large piezo-strain of the PMN-PT substrates, and (iii) effective elastic coupling at the film-substrate interface.

Influence of strain on the magnetization and magnetoelectric effect in La 0.7 A 0.3 Mn O 3 ∕ PMN − PT ( 001 ) ( A = Sr , Ca )

Effects of lattice strain on magnetic behavior of epitaxial La0.67Sr0.33MnO3 thin films grown by 90° off-axis sputtering have been studied. The size of epitaxial strain was varied using four different substrates, i.e., (001) LaAlO3, (001) SrTiO3, (001) La0.3Sr0.7Al0.65Ta0.35O9, and (110) NdGaO3. The observed magnetism of coherent epitaxial films grown on these substrates, particularly anisotropy and Curie temperature, exhibit strong correlations with lattice strains. Spin reorientation transitions have been observed. The dependence of Curie temperature on the bulk and Jahn–Teller strains has been determined.

Strain-dependent magnetic phase diagram of epitaxial La0.67Sr0.33MnO3 thin films

Manganese oxides (R, A)MnO3 (R = La, Y, Bi or rare earth metal, A = non-trivalent doping element) have been one focus of research for two outstanding properties: (i) conduction electrons (if any) are highly spin-polarized and (ii) competing interactions of several electronic and lattice degrees of freedom lead to extremely rich phase diagrams and complex physics. A better understanding of the latter might result in future technologies using manganites in spin-electronic devices. This review attempts to systematically outline in a phenomenological approach some fundamentals and key experiments on ferromagnetic manganites, partially with respect to thin film structures. Macroscopic magnetic properties (of ferromagnets and glassy manganites) and intrinsic electron transport are described. Preparation and basic properties of thin films, followed by experiments on spin-polarized tunnelling are reviewed. Finally, multiferroic heteroepitaxial film systems of manganites and ferroelectric titanates are addressed, which are promising candidates for significant magnetoelectric phenomena at ambient temperatures.

http://iopscience.iop.org/article/10.1088/0022-3727/39/7/R01/pdf

Ferromagnetic manganites: spin-polarized conduction versus competing interactions

Mixed-valence perovskite manganites (Re1-xAxMnO3 where Re = rare earth, A = alkaline earth) provide a unique opportunity to study the relationships between the structure and the magnetotransport properties due to an interplay among charge carriers, magnetic coupling, orbital ordering and structural distortion. This makes these compounds very exciting from both the basic research and from the technological viewpoint. As the technology pursued with these materials requires film growth, extensive studies have been made on materials synthesis, structural and physical characterization and device fabrication. In this article, the results from the different experimental techniques and the effects of the deposition procedure of the manganite thin films are first reviewed. Second, the relation between the structural and the physical properties is mentioned, and the influence of strains discussed. Finally, possible applications of manganite thin films in spin electronics are presented.

http://iopscience.iop.org/article/10.1088/0953-8984/13/48/201/pdf

Colossal magnetoresistive manganite thin films

Effect of grain size modulation on the magneto- and electronic-transport properties ofLa0.7Ca0.3MnO3nanoparticles: The role of spin-polarized tunneling at the enhanced grain surface

The evolution of three-dimensional strain states and crystallographic domain structures of epitaxial colossal magnetoresistive La0.8Ca0.2MnO3 films have been studied as a function of film thickness and lattice mismatch with two types of (001) substrates, SrTiO3 and LaAlO3. In-plane and out-of-plane lattice parameters and strain states of the films were measured directly using normal and grazing incidence x-ray diffraction techniques. The unit cell volume of the films is not conserved, and it exhibits a substrate-dependent variation with film thickness. Films grown on SrTiO3 substrates with thickness up to ∼250 A are strained coherently with a pure (001)T orientation normal to the surface. In contrast, films as thin as 100 A grown on LaAlO3 show partial relaxation with a (110)T texture. While thinner films have smoother surfaces and higher crystalline quality, strain relaxation in thicker films leads to mixed (001)T and (110)T textures, mosaic spread, and surface roughening. The magnetic and electrical tra...

Three-dimensional strain states and crystallographic domain structures of epitaxial colossal magnetoresistive la0.8ca0.2mno3 thin films

Magnetic anisotropy of La0.8Ca0.2MnO3 (LCMO) epitaxial thin films grown on (001) SrTiO3 and LaAlO3 a substrates exhibits strong correlation with substrate-induced strain states as determined by normal and grazing incidence x-ray diffraction. In a 250 A thick LCMO (001)T film grown on SrTiO3 substrate, an in-plane biaxial magnetic anisotropy is observed, and it is accompanied by a substrate-induced in-plane biaxial tensile strain. In contrast, the observed magnetic easy axis for a 250 A (110)T film grown on LaAlO3 substrate is perpendicular to the film plane, and the corresponding in-plane strain is biaxial compressive. In both cases the magnetic easy axes are along the crystallographic directions under tensile strain, indicating the presence of a positive magnetostriction. In thicker films (∼4000 A) grown on both substrates that are nearly strain relaxed, the magnetic easy axis lies in the film plane along the [110] direction of the (001) substrate.

Effect of three-dimensional strain states on magnetic anisotropy of La0.8Ca0.2MnO3 epitaxial thin films

The effects of strain relaxation on the crystallographic domain structure and on the magnetic and transport properties of epitaxial colossal magnetoresistive La0.8Ca0.2MnO3 (LCMO) thin films have been studied. LCMO films in the thickness range of 100–4000 A were grown on (001) SrTiO3 and (001) LaAlO3 substrates, which impose an in-plane tensile and an in-plane compressive biaxial stress in the films, respectively. On (001) SrTiO3 substrates, the films can be grown coherently up to a thickness ∼250 A, then strain relaxation occurs at a thickness of ∼500 A. In contrast, even the 100 A film grown on (001) LaAlO3 is partially relaxed, and the critical thickness for complete strain relaxation is ∼750 A. The very thin films (<250 A) show a pure (001)T normal orientation for growth on SrTiO3 and a pure (110)T texture for growth on LaAlO3. As thickness increases, the lattice strain relaxes, resulting in mixed (001)T and (110)T textures for growth on both substrates. Both the Curie and peak resistivity temperature...

Effects of film thickness and lattice mismatch on strain states and magnetic properties of La0.8Ca0.2MnO3 thin films

Magnetic anisotropy of epitaxial La0.8Ca0.2MnO3(LCMO) thin films grown by pulsed laser deposition has been studied as a function of temperature and lattice strain. Pseudomorphic growth on (001) SrTiO3 substrates imposes an in-plane tensile stress on the LCMO films, which produces an easy-plane magnetic anisotropy in the growth plane, accompanied by a weak biaxial anisotropy in the easy plane. In contrast growth on (001) LaAlO3 substrates produces an in-plane compressive stress, which leads to an out-of-plane uniaxial easy axis. The observed behavior indicates the presence of a positive magnetostriction, and that the anisotropy energy is dominated by the epitaxial strain induced effects. Uniaxial magnetic anisotropy constants of 250 and 500 A LCMO films have been determined by fitting the magnetization curves for temperatures between 5 and 200 K, and magnetostriction constants have been estimated subsequently.

Temperature dependence of magnetic anisotropy of La0.8Ca0.2MnO3 epitaxial thin films

The purpose of this study is to assess the effect of nine covariates on the occurrence or absence of stable or symptomatic pneumothorax. Forty-three patients underwent CT-guided lung biopsies from January 2020 to January 2022 (24 m, 19 f, median age 70 years). All the interventions were carried out with a semi-automatic 18G needle and a 17G trocar in a prone or supine position. Different covariates were measured and correlated to the rate and severity of the pneumothoraces observed. Nominal two-sided t-test p-values for the continuous variables and Fisher’s exact test results for the categorical variables were conducted. The data included the lesion size, distance to the pleura, needle-pleura angle, age, gender, position during the procedure, and the presence of chronic obstructive pulmonary disease. Patients with an observed pneumothorax had an average angle between the needle and the pleura of 74.00° compared to 94.68° in patients with no pneumothorax (p-value = 0.028). A smaller angle measurement correlated with a higher risk of pneumothorax development. The needle-pleural angle plays a vital role in the outcome of a CT-guided lung biopsy. Correctly adjusting the needle-pleural angle can diminish the pneumothorax risk associated with a CT-guided lung biopsy. The study results show that as the needle’s angle deviates from the perpendicular, the pleural surface area experiencing trauma increases, and pneumothorax is more likely to occur.

https://www.mdpi.com/2077-0383/11/7/1958/pdf?version=1648792742

D. Lavric

Papers

Three-dimensional strain states and crystallographic domain structures of epitaxial colossal magnetoresistive la0.8ca0.2mno3 thin films

Effect of three-dimensional strain states on magnetic anisotropy of La0.8Ca0.2MnO3 epitaxial thin films

Effects of film thickness and lattice mismatch on strain states and magnetic properties of La0.8Ca0.2MnO3 thin films

Temperature dependence of magnetic anisotropy of La0.8Ca0.2MnO3 epitaxial thin films

Associations between Covariates and Pneumothorax Observations in CT-Guided Lung Biopsies