Combined effect of magnetic field and hydrostatic pressure on the phase transitions exhibited by Ni-Mn-In metamagnetic shape memory alloy

We present a systematic study of the magnetostructural and magnetic transitions in the prototype metamagnetic shape memory alloy Ni50Mn34.5In15.5 under hydrostatic pressure and combined pressure and magnetic field. Pressure extends the area of stability of the antiferromagnetic martensitic phase. At low magnetic field the pressure derivatives of the Curie temperatures of austenite, TCA, and martensite, TCM, show opposite signs. This fact is described in the framework of the Landau thermodynamic model as arising from a weak long-range antiferromagnetic state of martensite. Two volume magnetoelastic constants were estimated using the experimental values of the pressure derivatives of TCA and TCM. A correlation between the signs of the pressure shifts of TCA, and TCM and the distance between Mn-Mn nearest neighbours is established, which matches the empirical Castelliz-Kanomata diagram. The entropy change at martensitic transformation (MT), ?SMT, grows up when the MT temperature, TM, is approaching TCA under the influence of pressure, but under constant non-zero pressure this dependence is inverse.The financial supports from Ministry of Science, Innovations and Universities (projects MAT2017-83631-C3-3-R and RTI2018-094683-B-C53-54) and from the Basque Government Department of Education (project IT1245-19) are greatly acknowledged

Синусный гистиоцитоз (болезньРозаи - Дорфмана): клиническое наблюдение

The authors characterized a heterogeneous group of a rare disease - Langerhans and non-Langerhans cell histiocytosis, and analyzed key differential and diagnostic differences between these forms of the disease. A very rare case of non- Langerhans cell histiocytosis (Rosai-Dorfman disease) in a female patient aged 63 with the subsequent spontaneous regression of eruptions was described. Key skin manifestations of the Rosai-Dorfman disease included papular eruptions of the typical intense pink color with a yellowish and brown tint. Morphologic changes were characterized by proliferation of histiocytes and accumulation of different lipids and pentalamellar markers (S-100 protein, СD 14, СD 68, lysozyme) in their cytoplasm. Though the Rosai-Dorfman disease usually involves lymph nodes, this case was characterized by unaffected nodular structures.Охарактеризована неоднородная группа редких гистиоцитозов лангергансового и нелангергансового типов; проанализированы их основные дифференциально-диагностические различия. Описано чрезвычайно редкое наблюдение гистиоцитоза нелангергансового типа (болезнь Розаи - Дорфмана) у пациентки 63 лет с последующим спонтанным регрессом высыпаний. Основные кожные проявления болезни Розаи - Дорфмана были представлены папулезными высыпаниями типичного насыщенного розового цвета с желтовато-коричневым оттенком. Морфологические изменения характеризовались пролиферацией гистиоцитов и накоплением в их цитоплазме различных липидов, пенталамеллярных маркеров (протеин S-100, СD14, СD 68, лизоцим). Несмотря на то что болезнь Розаи - Дорфмана, как правило, протекает с поражением лимфоузлов, отличительной особенностью данного наблюдения явилось отсутствие вовлечения нодулярных структур

Radiative Corrections for Pion Polarizability Experiments

We use the semi-analytical program RCFORGV to evaluate radiative corrections to one-photon radiative emission in the high-energy scattering of pions in the Coulomb field of a nucleus with atomic number Z. It is shown that radiative corrections can simulate a pion polarizability effect. The average effect was estimated for pion energies 40-600 GeV. We also study the range of applicability of the equivalent photon approximation in describing one-photon radiative emission.Comment: 11 pages (LaTex), 6 figures, 1 table. No changes in the paper. New submission because old files are corrupted in arXi

Stress-strain – Temperature behaviour for martensitic transformation in Ni-Mn-Ga single crystal compressed along <<001>> and <<110>> axes

The strain recovery upon heating pre-deformed martensite as well as the stress-strain behaviour in compression of parent phase of single crystalline Ni$_{49.4}$Mn$_{27.7}$Ga$_{22.9}$ alloy transforming martensitically at $T_M = 274$ K has been studied as a function of temperature and different orientation of compression axes. The constructed critical stress to induce the martensite transformation vs temperature ($\sigma_c-7$) phase diagrams can be represented by straight lines with slopes of $-2.5$ and $-9.4$ MPa/K in $$and$$ directions, respectively, which are in a good agreement with the theoretically estimated values

Time-dependent magnetostrain effect and stress relaxation in the martensitic phase of Ni-Mn-Ga

A simple theoretical model of the time-dependent magnetostrain effect in the Ni–Mn–Ga shape memory alloy is proposed. According to the model, a long-time response of the alloy to the magnetic field application is caused by the relaxation of field-induced mechanical stresses, and therefore, the field-induced strains depend exponentially on time. An agreement between the theoretical and experimental time dependencies of the field-induced strains is ascertained

Fluctuating stress as the origin of the time-dependent magnetostrain effect in Ni-Mn-Ga martensites

A recently observed phenomenon of the time-dependent deformation of ferromagnetic Ni-Mn-Ga martensites under a stationary magnetic field has been studied. A statistical model describing this phenomenon has been deduced from the mathematical theory of random processes. The influence of the duration of measurement on the shape of strain-field curves has been observed experimentally and interpreted in the statistical model framework of the time-dependent deformation. The evolution of deformation of the Ni-Mn-Ga alloy in the stepwise magnetic field has been considered. Good agreement between the theoretical and experimental results has been achieved for the suitable set of the model parameters

Магнітокалоричний ефект у метамагнітному сплаві з ефектом пам'яті форми

У даній статті представлені результати кількісного теоретичного аналізу прямого та оберненого магнітокалоричного ефекту (МКЕ) у метамагнітному сплаві з ефектом пам'яті форми (ММСЕПФ). Враховуючи нещодавно отримані експериментальні дані, що свідчать про антиферомагнітне упорядкування, був проведений теоретичний аналіз, який стартує з виразу для магнітної енергії антиферомагнетика з двома магнітними підгратками. Адіабатична зміна температури, зумовлена прямим та оберненим МКЕ в ММСЕПФ, була оцінена та порівняна з експериментальними даними, отриманими для сплаву Ni2Mn1.4Sn0.6. Адіабатична зміна температури залежить від зміни ентропії, спричиненої магнітним полем, і теплоємності сплаву. Для отримання кількісного узгодження між експериментальними та теоретичними даними були враховані та оцінені магнітний і немагнітний внески до теплоємності ММСЕПФ. Завдяки цьому був виявлений внесок спонтанної деформації, що супроводжує магнітоструктурний фазовий перехід, до загальної величини МКЕ. Також обчислено збільшення теплоємності, зумовлене зміною магнітного стану сплаву під час фазового переходу. Показано, що температурний пік теплоємності, спостережений в температурному інтервалі магнітоструктурного фазового перетворення сплаву Ni-Mn-Sn, є зумовленим як спонтанною деформацією кристалічної гратки, так і магнітним впорядкуванням сплаву. Показано, що наявність піку теплоємності зменшує очікувану з рівняння Дебая величину адіабатичної зміни температури у 2,5. Наскільки нам відомо, роль спонтанної деформації кристалічної гратки в температурній залежності теплоємності та оберненого МКЕ досі не розглядалася.In the present article, the results of quantitative theoretical analysis of the normal and inverse magnetocaloric effects (MCEs) in metamagnetic shape memory alloy (MMSMA) are reported. Taking into account that the direct experimental evidences of antiferromagnetic ordering were obtained recently, the theoretical analysis was carried out starting from the expression for the magnetic energy of antiferromagnet with two magnetic sublattices. The adiabatic temperature change caused by the inverse and normal MCEs in MMSMA was evaluated and compared with experimental data obtained for Ni2Mn1.4Sn0.6 alloy. The adiabatic temperature change depends on the magnetic-field-induced entropy change and heat capacity of the alloy. To obtain the quantitative agreement between the experimental and theoretical data the magnetic and non-magnetic contributions to the heat capacity of MMSMA were taken into account and evaluated. Due to this, the contribution of spontaneous deformation, which accompanies the magnetostructural phase transition, to the total value of MCE was discovered. The increase of heat capacity caused by the change of magnetic state of the alloy during the phase transition was computed as well. It was shown that the temperature peak of heat capacity, observed in the temperature range of magnetostructural phase transformation of Ni-Mn-Sn alloy, is caused by both spontaneous deformation of the crystal lattice and magnetic ordering of the alloy. It was shown that the presence of the peak of heat capacity diminishes the expected from the Debye equation value of adiabatic temperature change by factor 2.5. To the best of our knowledge, the role of spontaneous deformation of the crystal lattice in the temperature dependence of heat capacity and inverse MCE was not considered until now

Fluctuating stress as the origin of the time-dependent magnetostrain effect in Ni-Mn-Ga martensites

A recently observed phenomenon of the time-dependent deformation of ferromagnetic Ni-Mn-Ga martensites under a stationary magnetic field has been studied. A statistical model describing this phenomenon has been deduced from the mathematical theory of random processes. The influence of the duration of measurement on the shape of strain-field curves has been observed experimentally and interpreted in the statistical model framework of the time-dependent deformation. The evolution of deformation of the Ni-Mn-Ga alloy in the stepwise magnetic field has been considered. Good agreement between the theoretical and experimental results has been achieved for the suitable set of the model parameters