Ab initio study of electronic and magnetic structure and structural phase transition of (Fe 1-xMn x) 2P 1-yGe y alloys

The paper presents results of the ab initio electronic structure calculations performed for the (Fe0:5Mn0:5)2P0:67Ge0:33 alloy, a member of (Fe1xMnx)2P1yGey family of alloys showing a giant magnetocaloric e ffect. Calculations con rmed the strong relationship between the magnetic state and crystal structure of the alloy. To investigate the isostructural phase transition driven by external magnetic eld observed in (Fe0:9Mn1:1)P0:8Ge0:2 we utilized the xed spin moment approach. Total energy analysis con rmed the occurrence of isostructural phase transition

Ab Initio Study of Electronic and Magnetic Structure and Structural Phase Transition of (Fe1−xMnx)2P1−yGey(Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y} Alloys

The paper presents results of the ab initio electronic structure calculations performed for the $(Fe_{0.5}Mn_{0.5})_2P_{0.67}Ge_{0.33}$ alloy, a member of $(Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y}$ family of alloys showing a giant magnetocaloric effect. Calculations confirmed the strong relationship between the magnetic state and crystal structure of the alloy. To investigate the isostructural phase transition driven by external magnetic field observed in $(Fe_{0.9}Mn_{1.1})P_{0.8}Ge_{0.2}$ we utilized the fixed spin moment approach. Total energy analysis confirmed the occurrence of isostructural phase transition

Measurements of magnetic material parameters at alternative variants of magnetizing signal excitation

W artykule przedstawiono wyniki pomiarów parametrów próbek materiałów magnetycznych przy zastosowaniu różnych wariantów wymuszenia sygnału magnesującego. Sinusoidalne wymuszenie napięciowe sygnału powoduje sinusoidalne wymuszenie indukcji magnetycznej, co powoduje odkształcenie natężenia pola, natomiast sinusoidalne wymuszenie prądowe sygnału magnesowania powoduje sinusoidalne wymuszenie natężenia pola, co skutkuje odkształceniem indukcji (strumienia magnetycznego). Porównano parametry podstawowych parametrów opisujących właściwości materiałów magnetycznych badanych próbek otrzymane dla dwóch wariantów wymuszeń pola.The parameters of magnetic materials are determined by both the autonomic measuring stands, i.e. the volt-ampermeter method and the impedances bridges or the computer measuring systems. The sources of signal in measuring system to investigation of magnetic material parameters are alternating current power supplies. However, in automated measuring systems, the final unit of track feeding is power amplifier. It permits to extorting both the proper value of voltage and to supply the tested sample appropriate large current. The Polish Standard allows two variants of sinusoidal signal ex-tortion to investigation of magnetic materials. First of them is sinusoidal extortion of magnetic flux density B while the second variant admits to sinusoidal signal extortion of field intensity H into the tested sample. Extortion from theoretically ideal voltage source signal corresponds to the first option, while in the second variant is necessary ideal current source. In practice, to comply with requirement of the Standard, it is necessary to assure the condition of a much smaller or a much larger internal source impedance in relation to impedance of magnetizing winding of the test sample, respectively to condition of voltage or current extortion. Disposing of either the power supply with well-known internal impedance or the amplifier with well-known output impedance this condition be comply with properly selection of magnetizing winding number of turns. The investigation of magnetic materials of different samples in which was executed either the force of sinusoidal magnetic flux density, which effects the deformation of intensity of the field strength or sinusoidal force of the field strength which causes the deformation of magnetic flux is presented. The essential parameters of the magnetic materials of the test samples to obtain by means of two variants input signal force were compared. The investigations showed distinctness of measurements results of parameters of the same samples by applying the different variants of signal extortions admitted by the Standard

Giant Magnetocaloric Effect in Manganites

In this review we briefly discuss the magnetocaloric properties of the manganites. It is evidenced that the maximum entropy change observed in manganites exceeds that of gadolinium (the prototype material for room temperature refrigerators). For the manganites characterized by second-order magnetic phase transitions the scaling hypothesis is discussed. It is shown that simple phenomenological model with only one fitting parameter, presented in this paper, satisfactorily describes experimental observations

Fabrication of the FeNbCuSiB amorphous ribbons based on a molten metal transport onto a bottom surface of rotating wheel

W artykule przedstawiono nową metodę wytwarzania taśm amorficznych poprzez ultraszybkie schładzanie ciekłego stopu na dolnej powierzchni wirującego bębna metalowego. Opisano zasadę działania eksperymentalnego urządzenia odlewniczego zaprojektowanego i zbudowanego w Instytucie Metali Nieżelaznych w Gliwicach oraz wyniki dotychczas przeprowadzonych testów ze szczególnym uwzględnieniem problemu transportu ciekłego metalu na dolną powierzchnię bębna. Wyniki badań otrzymanych taśm potwierdziły ich dobre właściwości mechaniczne, strukturalne i magnetycznie miękkie.A new fabrication method of amorphous ribbons by rapid quenching of a liquid metal on a bottom surface of rotating copper wheel has been presented. Principle of operation of an experimental casting installation designed and built at the Institute of Non-Ferrous Metals in Gliwice, Poland, has been described together with results of tests carried out so far, with a special emphasis put on the problem of transporting molten metal onto a bottom surface of a wheel. Examination of the amorphous ribbons obtained confirmed their good mechanical, structural and soft magnetic properties

Dynamic Magnetic Properties of the Magnetostrictive Rapidly-Quenched Alloys

This work was aimed at investigating the FeNbCuSiB and FeNiMoB type alloys exhibiting relatively high saturation magnetostriction after suitable heat treatment, which makes them suitable for application in force sensors. Samples of both alloys were prepared in a form of toroidal cores wound from amorphous ribbons obtained by melt-spinning, and then the cores were annealed under longitudinal and transverse magnetic field. An effect of the induced magnetic anisotropy and of the applied compressive stresses on the dynamic magnetic properties of both alloys within a frequency range from 50 Hz to 50 kHz was studied

New Method of Measurement of the Magnetoelastic Characteristics for Tensile Stresses

The paper presents a novel method of measurements of tensile stress dependence of the magnetic characteristics of ring-shaped cores made of soft amorphous alloys. In the presented method, the uniform tensile stress was applied perpendicularly to the magnetizing field direction. Magnetoelastic core with closed magnetic circuit was fixed on the non-magnetic backings enabling the conversion of compressive force into tensile stresses as well as it enables the core to be winded by magnetizing and sensing windings. Magnetoelastic characteristics measured under tensile stress, for $Fe_{25}Ni_{55}Si_{10}B_{10}$ alloy annealed in temperature 350°C for 1 h, are presented in this paper. The presented results indicate high tensile stress sensitivity of $Fe_{25}Ni_{55}Si_{10}B_{10}$ alloy. Moreover, together with magnetoelastic characteristics for compressive stresses (presented previously in the literature), the describes results create possibility of further development of models of the magnetoelastic effects in amorphous alloys

Origin of Magnetic Anisotropy of Gd5Si2Ge2Gd_{5}Si_{2}Ge_{2} Compound

The second-order anisotropy constant $K_2$ in polycrystalline $Gd_5Si_2Ge_2$ giant magnetocaloric material was measured as a function of temperature by the modified singular point detection technique. Although the structural, electrical, thermal, magnetic and magnetocaloric properties of the $Gd_5Si_2Ge_2$ have been rather well investigated experimentally, magnetic anisotropy of this system is almost unknown. The singularity indicating the anisotropy field was determined analyzing ac susceptibility data taking into account several features of the magnetization curve. The temperature dependence of the anisotropy fields was measured from 4.2 K up to the Curie temperature. The observed relationship between $K_2 (T)//K_2$ (0) and magnetization M (T)/M (0) was explained assuming dipolar origin of magnetic anisotropy of $Gd_5Si_2Ge_2$ compound

Utilizing of magnetic amorphous alloys in magnetoelastic tensile stress sensors

W referacie omówiono możliwości wykorzystania stopów amorficznych o składzie Fe77Cr2B16Si5 do budowy sensorów sił rozciągających. W opracowanych sensorach uzyskano równomierny rozkład naprężeń rozciągających działających w kierunku osi magnesowanego rdzenia pierścieniowego. Przedstawione wyniki wykazały wysoką czułość magnetosprężystą stopu o składzie Fe77Cr2B16Si5, poddanego działaniu naprężeń rozciągających. Ponadto stwierdzono, że czułość magnetosprężysta rośnie w wyniku przeprowadzenia relaksacji termicznej - wyżarzania stopu amorficznego.Paper presents possibilities of utilizing Fe77Cr2B16Si5 amorphous alloy in development of magnetoelastic tensile stresses sensors. In presented sensors the uniform distribution of tensile stresses was achieved. These stress were perpendicular to the direction of magnetizing field in the ring-shaped core. Presented results indicated high magnetoelastic sensitivity of Fe77Cr2B-16Si5 amorphous alloy under tensile stresses. Moreover it was indicated, that magnetoelastic sensitivity increases due to thermal relaxation - annealing of amorphous core