Buffer influence on magnetic dead layer, critical current and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy

We present a thorough research on Ta/Ru-based buffers and their influence on features crucial from the point of view of applications of MTJs, such as critical switching current and thermal stability. We investigate devices consisting of buffer/FeCoB/MgO/FeCoB/Ta/Ru multilayers for three different buffers: Ta 5 / Ru 10 / Ta 3, Ta 5 / Ru 10 / Ta 10 and Ta 5 / Ru 20 / Ta 5 (all thicknesses in nm). In addition, we study systems with a single FeCoB layer deposited above as well as below the MgO barrier. The crystallographic texture and the roughness of the buffers are determined by means of XRD and atomic force microscopy measurements. Furthermore, we examine the magnetic domain pattern, the magnetic dead layer thickness and the perpendicular magnetic anisotropy fields for each sample. Finally, we investigate the effect of the current induced magnetization switching for nanopillar junctions with lateral dimensions ranging from 1 {\mu}m down to 140 nm. Buffer Ta 5 / Ru 10 / Ta 3, which has the thickest dead layer, exhibits a large increase in the thermal stability factor while featuring a slightly lower critical current density value when compared to the buffer with the thinnest dead layer Ta 5 / Ru 20 / Ta 5

Własności fizyczne stopów Ti45Zr38Ni17-xMx (M = Co, Fe, Mn) i Ti48Zr7Fe18 oraz ich wodorków rozprawa doktorska /

Tyt. z ekranu tytułowego.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2011.Zawiera bibliogr.Dostępna także w wersji drukowanej.Tryb dostępu: Internet.Charakterystyka kwazikryształów, materiałów amorficznych, kwazikryształy, tworzenie się faz kwazikrystalicznych, rodzaje kwazikryształów, rozmieszczenie atomów w kwazikryształach, klastery w kwazikryształach ikosaedrycznych, sposoby wytwarzania kwazikryształów, amorficzne stopy metali, wodór w stopach Ti-Zr-Ni w fazie amorficznej, kwazikrystalicznej, formowanie fazy kwazikrystalicznej stopu Ti45Zr38Ni17, wodór w strukturze fazy kwazikrystalicznej, lokalizacja wodoru w strukturze, absorpcja wodoru w stopie Ti45Zr38Ni17, desorpcja wodoru w fazie amorficznej, kwazikrystalicznej, metody badawcze, preparatyka próbek, pomiary dyfrakcyjne, równanie Bragga, natężenia wiązek ugiętych w promieniowaniu rentgenowskim, w dyfrakcji neutronów, dyfrakcja jądrowa, magnetyczna, porównanie dyfrakcji neutronów, rentgenowskiej, podstawowe parametry dyfraktometru Siemens D5000, stanowisko pomiarowe dyfrakcji neutronów, pomiar techniką EXAFS, promieniowanie synchrotronowe, metoda EXAFS, stanowisko pomiarowego CEMO, Hasylab/DESY, spektroskopia Mössbauerowska, pomiary termiczne, różnicowa kalorymetria skaningowa, DSC, opis stanowiska pomiarowego DSC-60, spektroskopia desorpcji termicznej, opis pomiarów na stanowisku TDS, wyniki badań, ich interpretacja, badanie podstawowego stopu Ti45Zr38Ni17, pomiary dyfrakcyjne, dyfrakcja rentgenowska stopu w fazie amorficznej, stopu w fazie kwazikrystalicznej, pomiary termiczne, różnicowa kalorymetria skaningowa, pomiar desorpcji wodoru, dyfrakcja neutronów, obserwacja przemiany fazy amorficznej w fazę kwazikrystaliczną stopu Ti45Zr38Ni17, dyfrakcja neutronów podczas uwalniania deuteru z deuterków fazy amorficznej stopu Ti45Zr38Ni17, dyfrakcja neutronów podczas desorpcji deuteru z deuterku fazy kwazikrystalicznej stopu Ti45Zr38Ni17, wnioski dla stopu Ti45Zr38Ni17, badanie stopów podstawianych żelazem, Ti45Zr38Ni17-xFex (x = 4, 8), pomiary dyfrakcji rentgenowskiej, dyfrakcja rentgenowska w fazie amorficznej, kwazikrystalicznej, pomiary termiczne, różnicowa kalorymetria skaningowa, badanie desorpcji wodoru, wnioski dla stopów podstawianych żelazem, badanie stopów podstawianych kobaltem - Ti45Zr38Ni17-xCox (x = 4, 8), pomiary dyfrakcji rentgenowskiej, różnicowa kalorymetria skaningowa, badanie desorpcji wodoru, pomiary techniką EXAFS, wnioski dla stopów podstawianych kobaltem, badania stopów podstawianych manganem - Ti45Zr38Ni17-xMnx (x = 2, 4), pomiary dyfrakcje, różnicowa kalorymetria skaningowa, badanie desorpcji wodoru, wnioski dla stopów podstawianych manganem, badanie stopu Ti48Zr7Fe18, badanie desorpcji wodoru z nawodorowanej fazy amorficznej stopu Ti48Zr7Fe18, spektroskopia Mössbauerowska stopu Ti48Zr7Fe18, zawartość wodoru w badanych stopach, porównanie właściwości badanych materiałó

Surface-Step-Induced Magnetic Anisotropy in Epitaxial LSMO Deposited on Engineered STO Surfaces

Changes in stoichiometry, temperature, strain and other parameters dramatically alter properties of LSMO perovskite. Thus, the sensitivity of LSMO may enable control of the magnetic properties of the film. This work demonstrates the capabilities of interface engineering to achieve the desired effects. Three methods of preparing STO substrates were conducted, i.e., using acid, buffer solution, and deionized water. The occurrence of terraces and their morphology depend on the preparation treatment. Terraces propagate on deposited layers and influence LSMO properties. The measurements show that anisotropy depends on the roughness of the substrate, the method of preparing the substrate, and oxygen treatment. The collected results suggest that the dipolar mechanism may be the source of LSMO anisotropy

The Effect of a Multiphase Microstructure on the Inverse Magnetocaloric Effect in Ni–Mn–Cr–Sn Metamagnetic Heusler Alloys

Two Ni–Mn–Sn alloys substituted with 0.5 and 1 at.% Cr have been studied. The first alloy shows an average composition of Ni49.6Mn37.3Cr0.7Sn12.4 (e/a = 8.107), whereas the second has a multiphase microstructure with the matrix phase of an average Ni52.4Mn32.7Cr1Sn14 composition (e/a = 8.146). Both alloys undergo a reversible martensitic phase transformation. The Ni49.6Mn37.3Cr0.7Sn12.4 alloy transforms to the martensite phase at 239 K and, under the magnetic field change of μ0·ΔH = 1.5 T, gives the magnetic entropy change equal to 7.6 J/kg·K. This amounts to a refrigerant capacity in the order of 48.6 J/kg, reducible by 29.8% due to hysteresis loss. On the other hand, the alloy with a multiphase microstructure undergoes the martensitic phase transformation at 223 K with the magnetic entropy change of 1.7 J/kg·K (1 T). Although the latter spreads over a broader temperature window in the multiphase alloy, it gives much smaller refrigerant capacity of 16.2 J/kg when compared to Ni49.6Mn37.3Cr0.7Sn12.4. The average hysteresis loss for a field change of 1.5 T in the multiphase alloy is 2.7 J/kg, reducing the effective refrigerant capacity by 16.7%. These results illustrate that the key to gaining a large effective refrigerant capacity is the synergy between the magnitude of the magnetic entropy change and its broad temperature dependence

Physical Properties of Ti₄₅Zr₃₈Fe₁₇ Alloy and Its Amorphous Hydride

The alloys based on Ti-Zr are considered an excellent candidate for hydrogen storage applications. In this communication, we report the results of Fe substitution for Ni in the well-known Ti45Zr38Ni17 compound. The parent and related compounds can be obtained as amorphous powders, transforming into the quasicrystalline phase (i-phase) after annealing. The amorphous Ti45Zr38Fe17 phase is transformed into the icosahedral quasicrystalline state, and it is a quasi-continuous process. The i-phase is well-developed close to 500 °C. At higher temperatures, the quasicrystal structure transforms into the other phase: the w-phase (an approximant to the crystalline phase) and another crystal phase with a small addition of the FeZr3 and the Fe2(ZrTi)3. The amorphous Ti45Zr38Fe17 phases can be hydrogenated while maintaining the amorphous nature, which constitutes another very fascinating research field for our group. The investigated alloy shows a good capacity for gaseous H2 at level 2.54 wt.% at elevated temperatures. The ferromagnetic signal of the amorphous TiZrFe comes from magnetic nanocrystallites in the amorphous matrix. After heating, the magnetic signal significantly decreases due to the lack of long-range magnetic ordering in the i-phase of the Ti45Zr38Fe17 alloy

Physical Properties of Ti45Zr38Fe17 Alloy and Its Amorphous Hydride

The alloys based on Ti-Zr are considered an excellent candidate for hydrogen storage applications. In this communication, we report the results of Fe substitution for Ni in the well-known Ti45Zr38Ni17 compound. The parent and related compounds can be obtained as amorphous powders, transforming into the quasicrystalline phase (i-phase) after annealing. The amorphous Ti45Zr38Fe17 phase is transformed into the icosahedral quasicrystalline state, and it is a quasi-continuous process. The i-phase is well-developed close to 500 °C. At higher temperatures, the quasicrystal structure transforms into the other phase: the w-phase (an approximant to the crystalline phase) and another crystal phase with a small addition of the FeZr3 and the Fe2(ZrTi)3. The amorphous Ti45Zr38Fe17 phases can be hydrogenated while maintaining the amorphous nature, which constitutes another very fascinating research field for our group. The investigated alloy shows a good capacity for gaseous H2 at level 2.54 wt.% at elevated temperatures. The ferromagnetic signal of the amorphous TiZrFe comes from magnetic nanocrystallites in the amorphous matrix. After heating, the magnetic signal significantly decreases due to the lack of long-range magnetic ordering in the i-phase of the Ti45Zr38Fe17 alloy

High-Entropy Perovskite Thin Film in the Gd-Nd-Sm-La-Y-Co System: Deposition, Structure and Optoelectronic Properties

Multicomponent equimolar perovskite oxides (ME-POs) have recently emerged as a highly promising class of materials with unique synergistic effects, making them well-suited for applications in such areas as photovoltaics and micro- and nanoelectronics. High-entropy perovskite oxide thin film in the (Gd0.2Nd0.2La0.2Sm0.2Y0.2)CoO3 (RECO, where RE = Gd0.2Nd0.2La0.2Sm0.2Y0.2, C = Co, and O = O3) system was synthesized via pulsed laser deposition. The crystalline growth in an amorphous fused quartz substrate and single-phase composition of the synthesized film was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Surface conductivity and activation energy were determined using a novel technique implementing atomic force microscopy (AFM) in combination with current mapping. The optoelectronic properties of the deposited RECO thin film were characterized using UV/VIS spectroscopy. The energy gap and nature of optical transitions were calculated using the Inverse Logarithmic Derivative (ILD) and four-point resistance method, suggesting direct allowed transitions with altered dispersions. The narrow energy gap of RECO, along with its relatively high absorption properties in the visible spectrum, positions it as a promising candidate for further exploration in the domains of low-energy infrared optics and electrocatalysis