Correlation between magnetic and crystal structural sublattices in palladium-doped FeRh alloys: Analysis of the metamagnetic phase transition driving forces

FeRh alloys doped with the third element exhibit a change in the lattice and magnetic subsystems, which are manifested in antiferromagnetic- ferromagnetic (AFM-FM) first-order phase transition temperature, the shrinkage of the temperate hysteresis under transition, and the reduction of the saturation magnetization. All aforementioned parameters are crucial for practical applications. To control them it is quite important to determine the driving forces of the metamagnetic transition and its origins. In this manuscript ab initio calculations and experimental studies results are presented, which demonstrate the correlation between the structural and magnetic properties of the Fe50Rh50−xPdx alloys. The qualitative analysis of the metamagnetic phase transition driving forces in palladium-doped FeRh alloys was performed to determine their contribution to the evolution of magnetic and lattice subsystems. In addition, the impact of the impurities phases together with its magnetic behavior on the AFM-FM phase transition was considered.Fil: Komlev, Aleksei S.. Lomonosov Moscow State University; RusiaFil: Karpenkov, Dmitriy Y.. National University of Science and Technology; Rusia. Lomonosov Moscow State University; RusiaFil: Gimaev, Radel R.. Lomonosov Moscow State University; RusiaFil: Chirkova, Alisa. Institute for Materials Science; AlemaniaFil: Akiyama, Ayaka. Hirosaki University; JapónFil: Miyanaga, Takafumi. Hirosaki University; JapónFil: Hupalo, Marcio Ferreira. Universidade Estadual do Ponta Grossa; BrasilFil: Aguiar, D.J.M.. Universidade Federal do Paraná; BrasilFil: Carvalho, Alexandre Magnus G.. Universidade Estadual de Maringá; Brasil. Universidade Federal de Sao Paulo; BrasilFil: Jiménez, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Cabeza, Gabriela Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Zverev, Vladimir I.. Lomonosov Moscow State University; RusiaFil: Perov, Nikolai S.. Lomonosov Moscow State University; Rusi

Peculiarities of the Phase Transformation Dynamics in Bulk FeRh Based Alloys from Magnetic and Structural Measurements

We analyze coexistence of antiferromagnetic and ferromagnetic phases in bulk iron-rhodium and its alloys with palladium, Fe50,4Rh49,6, Fe49,7Rh47,4Pd2,9 and Fe48,3Rh46,8Pd4,9, using neutron diffraction, magnetization and scanning Hall probe imaging. Temperature dependencies of the lattice parameters, AFM and FM phase weight fractions, and Fe magnetic moment values were obtained on cooling and heating across the AFM-FM transition. Substantial thermomagnetic hysteresis for the phases’ weight fractions and a relatively narrow one for the unit cell volume has been observed on cooling-heating. A clear dependence of hysteretic behavior on Pd concentration has been traced. Additional direct magnetic measurements of the spatial distribution of the phase transition are acquired using scanning Hall probe microscopy, which reveals the length scale of the phase coexistence and the spatial progression of the transition in the presence of external magnetic field. Also, the magnetic phase diagram has been constructed for a series of Pd-doped FeRh alloys. © 2020 Elsevier B.V.EL acknowledges funding from the UK EPSRC. LFC acknowledges funding from the EPSRC and InnovateUK: Project number: 105541. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was partly supported by the state assignment of the Ministry of Science and Higher Education (themes “Flux” No. AAAA-A18-118020190112-8 and “Alloys” № AAAA-A19-119070890020-3)

The effect of cooling rate on magnetothermal properties of Fe49Rh51

We have investigated the effects of quenching rate on the thermal dependence of the magnetic entropy change ΔSM(T) and the magnetic field induced hysteresis loss through the antiferromagnetic (AFM) ↔ ferromagnetic (FM) transformation in bulk Fe49Rh51. Two nearly identical square-prism-shaped samples were subjected to two different temperature cooling regimes; one was rapidly quenched (FQ) in iced-water and another slow cooled (SC) to room temperature at a cooling rate of 2 K/min. The temperature of the AFM ↔ FM transition is similar for both samples, but the FQ sample shows much sharper temperature- and magnetic field-induced magnetization change; in addition, the total magnetization change is 14% larger. In FQ material, the magnetocaloric effect, i.e., ΔSM(T) quickly approaches saturation above 1 T and shows a large peak value at 2 T (13.9 versus 8.9 Jkg−1 K−1 in SC material), but a larger average hysteresis loss \u3cHL\u3eFWHM in the temperature range coinciding with of the full-width at half-maximum of the ΔSM(T) curve

Structural-electrical remodeling of myocardium in neurological deficits in patients with ischemic stroke: is there a connection?

Abstract Funding Acknowledgements Type of funding sources: None. Theoretical and clinical questions of the correlation between structural-electrical remodeling of the heart and the severity of neurological deficits at stroke have not been developed or remain controversial so far.  Available data in the literature suggests the key role of structural myocardial disorders mainly in hemorrhagic stroke, and cardiocerebral syndrome is considered only from the standpoint of cardioembolic stroke. The aim of the study.  To study the peculiarities of structural-electrical remodeling of myocardium with severity of neurological deficit in patients with ischemic stroke. Materials and methods.  111 patients with ischemic stroke in the left hemisphere and 75 patients in the right brain hemisphere were examined. The average age was 56.7 ± 5.58 years. All subjects underwent an ultrasound examination of the heart using the ALOKA SSD 5000 apparatus (Japan) and the QT dispersion using the Polyspectro-8EX apparatus (Russia). Duration of QT dispersion interval more than 50 ms was considered pathological. Research results.  Structural remodeling of the heart in patients with ischemic stroke was manifested by the prevalence of high values of the finite-systolic volume of the left ventricle in comparison with patients without stroke (45.8 ± 21.0 vs. 37.7 ± 16.9 ml; p &amp;lt; 0.05), and the finite-diastolic volume of the left ventricle (114.3 ± 38.5 vs. 100.9 ± 35.3 ml; p &amp;lt; 0.05), mainly in the right hemispheric localization of the stroke. Hypertrophy of the ventricular septum (11.3 ± 2.1 and 11.1 ± 2.2) and the posterior wall of the left ventricle (10.4 ± 1.8 and 10.3 ± 2.1 mm) was observed irrespective of the localization of the stroke, which was higher in comparison with patients without stroke (9.4 ± 1.5 mm). Violations of repolarization processes and their severity were characterized by higher values of duration of the corrected QT interval in patients with structural changes of myocardium in comparison with the patients without structural remodeling (0,46 ± 0,03 and 0,44 ± 0,02 sec; p = 0,025).  The conjugation of the severity of the neurological deficit (7 and more points on the NIHSS scale) was associated with the terminal-systolic size of the LV (p = 0.025) and myocardial hypertrophy (11.3 ± 1.86 vs. 10.96 ± 1.8 mm; p = 0.04) in comparison with patients with a neurological deficit of less than 7 points (31.7 ± 3.6 vs. 30.68 ± 3.86 mm; p &amp;lt; 0.025).  The severity of the neurological deficit according to the Goldstein criteria correlated with higher values of the corrected (56.0 ± 23.93 vs. 41.6 ± 23.3 ms.; p = 0.043) and normalized QT (17.5 ± 6.533 vs. 12.8 ± 6.7 ms.; p = 0.019) values in comparison with the lower neurological deficit. A similar relationship was revealed by the Brott criteria. Conclusions.  Thus, the direct connection between structural-electrical remodeling of the heart and neurological deficit revealed in the course of the study reflects the cardiocerebral relationships in ischemic stroke. </jats:sec

Electric myocardial inhomogeneity and stroke: connection and specifics

Abstract Funding Acknowledgements Type of funding sources: None. Background. The inconsistency of the literature data on the influence of different hemispheric localization of Cerebrovascular accident (CVA) on the development of cardiac arrhythmias suggests the expediency of further study of the so-called "zones" of the cerebral cortex associated with electrical instability of the myocardium.  It is known that dispersion of QT interval and fragmented myocardial activity belong to the markers of electrical instability of the heart and are associated with arrhythmogenesis.  The aim of the study.  To study the severity of abnormalities of the parameters of electrical instability of myocardium in right and left hemispheric stroke localization in patients with hypertension. Material and methods. 111 patients with left hemispheric localization of ischemic stroke and 75 patients with right hemispheric stroke were examined. Hemorrhagic stroke was observed in 17 patients in the left hemisphere and in 13 patients in the right hemisphere. The average age was 58,2 ± 7,48 years. For all strokes, men prevailed (64% vs. 36%). For the first day of the stroke, all patients were evaluated for QT dispersion and fragmented myocardial activity on the device "Polyspectro-8EX" (Russia).  Research results.  Evaluation of the parameters of electrical instability of myocardium in patients with stroke revealed more pronounced disorders in hemorrhagic stroke of left hemispheric localization (Table 1). In ischemic stroke, the severity of electrophysiological parameters, reflecting the instability of the myocardium depending on the hemispheric localization, indicates the absence of differences.  Conclusions.  1.The most pronounced disturbances in the parameters of electrical stability of the myocardium is observed in hemorrhagic stroke.  2.The severity of myocardial electrical instability in ischemic stroke is not associated with the localization of the focus. </jats:sec

P1569 Left ventricle structure and function relations with renin-angiotensin-aldosteron system activity and plasma markers of fibrosis in patients with ACS underwent PCI

Abstract Renin-angiotensin-aldosterone system (RAAS) plays significant role in development of myocardial fibrosis and LV remodelling which may increase severity of stroke and myocardial infarction. The purpose of the study is to evaluate relations between activity of RAAS and left ventricle structure and function in patients with acute coronary syndrome (ACS) underwent PCI. We examined 204 patients (both men and women) with ACS which were undergoing PCI. The mean age of patients was 51.0 (11) years. In all patients was performed ECG in 12 leads; EchoCG; evaluation plasma levels of aldosterone, angiotensin 2 (AT2), angiotensin-converting enzyme (ACE), tissue inhibitor of metalloproteinases-1 (TIMP-1) and insulin-like growth factor 1 (IGF-1). Statistical significance was defined at the level of methods for p &amp;lt; 0,05. Results of correlative analysis revealed relations between ILV mass and aldosterone (R = 0.57; p &amp;lt; 0.001), ACE (R = 0.59; p &amp;lt; 0.001), AT2 (R = 0.58; p &amp;lt; 0.001) and TIMP-1 (R = 0.54; p &amp;lt; 0.001). There were relations between E/A and AT2 (R = 0.23; p = 0.049), TIMP-1 (R = 0.22; p = 0.038); between IGF-1 and DT (R = 0.21; p = 0.045). This could be due to the growth in fibroblasts and cardiaomyocytes and increase in myocardial stiffness. The results of the comparison of RAAS activity markers, structural and functional parameters of the LV in patients with different LV geometry can be seen in Table 1. Thus, the results of the study show that activation of RAAS leads to increase in myocardial stiffness; and that RAAS activity and plasma markers of fibrosis was significantly higher in patients with concentric and eccentric LV hypertrophy. RAAS activity &amp; LV geometry and function Parameters LV geometry models Normal Geometry n = 25 Concentric Remodelling n = 18 Concentric Hypertrophy n = 89 Eccentric Hypertrophy n = 72 Angiotensin 2 (pg/ml) 36.2 (11.6) 28.2 (5.5) 58.4 (46.; 64.5)*†‡ 45.8 (13.2)*† ACE (u/l) 44.4 (17.4) 30.3 (20.1; 33.0)* 67.6 (28.3)*† 57.1 (39.0; 68.0)† Aldosterone (pg/ml) 111.0 (76.8; 136.6) 101.2 (80.0; 120.5)* 152.4 (135.2; 177.3)*†‡ 136.0 (129.0; 152.0)*† TIMP-1 (ng/ml) 222.9 (80.9) 237.5 (140.0; 322.0)* 358.0 (259.0; 493.0)*†‡ 329.2 (102.5)*† IGF-1 (ng/ml) 174.2 (25.1) 174.5 (160.0; 179.0) 146.0 (129.0; 167.0)*† 148.9 (20.7)*† ILV mass (g/m&amp;sup2;) 85.0 (79.1; 92.4) 94.7 (92.4; 97.9)* 146.3 (127.0; 171.1)*†‡ 127.0 (115.7; 149.0)*† E/A 0.7 (0.1) 0.8 (0.7; 0.9) 0.9 (0.8; 1.2)* 0.9 (0.8; 1.1)*† DT (ms) 194.3 (22.2) 185.4 (19.5) 198.9 (44.3)† 179.1 (26.8) E/e" 8.0 (0.9) 6.1 (5.4; 8.6)* 6.9 (5.5; 9.2)* 8.8 (3.0)† * - p &amp;lt; 0.05 in comparison with patients with normal geometry; † - p &amp;lt; 0.05 in comparison with patients with concentric remodelling; ‡ - p &amp;lt; 0.05 in comparison with patients with eccentric hypertrophy. </jats:sec

Spontaneous platelet aggregation in patients with chronic heart failure with arterial hypertension

Abstract Funding Acknowledgements Type of funding sources: None. Aim of study. To study spontaneous platelet aggregation in patients with arterial hypertension with different functional classes (FC) of CHF with preserved systolic function not taking antiplatelet therapy. Material and Methods 51 patients with AH with different types of CHF, mean age 55.4 ± 5.9 years, with preserved left ventricular systolic function according to ECHO-CS were studied. The patients were divided into 4 groups depending on FC of CHF: Group 1 - 0 FC of CHF (n = 11), Group 2 - 1 FC of CHF (n = 13), Group 3 - 2 FC of CHF (n = 14), and Group 4 - 3 FC of CHF (n = 13). Spontaneous platelet aggregation was determined on a KFK-2MP photoelectrocolorimeter (Russia). Results. During the study, the spontaneous platelet aggregation was 1.08 ± 0.31 in patients with CHF class 0 (1 gr), and 1.22 ± 0.25 in patients with CHF class 1, with no statistical difference in comparison with 1 gr (p = 0.233). In group 3 (2FC CHF), spontaneous platelet aggregation was 1.33 ± 0.27, with a statistically significant difference with spontaneous platelet aggregation in patients with type 0 (p = 0.042), but with group 2 (1FC CHF), no statistically significant difference was found (p = 0.281). Spontaneous platelet aggregation in group 4 (3FC CHF) was 1,62 + 0,32, with statistically significant difference in comparison with all groups, so with group 1 - p &amp;lt; 0,001, with group 2 - p = 0,016 and with group 3 - p = 0,017. Conclusion. Patients with arterial hypertension with preserved systolic function showed an increase in spontaneous platelet aggregation with increasing functional class of CHF, and the most significant increase in platelet aggregation was seen in patients with class 3 CHF. </jats:sec