Взаємний зв'язок властивостей і структури плівкових чутливих елементів сенсорів магнітного поля

Дисертацію присвячено комплексним експериментальним дослідженням особливостей структурно-фазового стану та магнітних і магніторезистивних властивостей багатошарових плівкових систем на основі Co і Cu, Co і Cr, Fe і Cr та Fe і Cu як можливих матеріалів чутливих елементів сенсорів різного призначення. У роботі встановлено взаємозв’язок між товщиною магнітних шарів і немагнітних прошарків, орієнтацією зразка у зовнішньому магнітному полі, температурою термообробки та магнітними, магніторезистивними і магнітооптичними властивостями багатошарових плівкових систем із можливим спін-залежним розсіюванням електронів. Визначені величини магнітоопору, коерцитивної сили, коефіцієнта прямокутності й чутливості плівкової системи до магнітного поля досліджуваних плівкових систем як приладових структур для формування первинних перетворювачів. Установлена кореляція між структурно-фазовим станом, магнітними та магнітооптичними властивостями тришарових плівкових систем з різним типом розчинності компонент як функціональних елементів датчиків. Запропонована схематична конструкція АМР-датчика магнітного поля для тришарових плівкових систем із спін-залежним розсіюванням електронів. У результаті проведених досліджень впливу геометрії вимірювання, температури термообробки та загальної концентрації феромагнітної компоненти в системі на магнітні й магніторезистивні властивості визначені можливі області застосування плівкових систем на основі Co і Cu або Cr та Fe і Cu або Cr.Диссертация посвящена комплексным экспериментальным исследованиям особенностей структурно-фазового состояния, магнитных магниторезистивных свойств многослойных пленочных систем на основе Co и Cu, Co и Cr, Fe и Cr и Fe и Cu в качестве возможных материалов чувствительных элементов сенсоров различного назначения. В работе установлена взаимосвязь между толщиной магнитных слоев и немагнитных прослоек, ориентацией образца во внешнем магнитном поле, температурой термообработки и магнитными, магниторезистивными и магнитооптическими свойствами многослойных пленочных систем с возможным спин-зависимым рассеянием электронов. При исследовании магнитных свойств пленочных систем на основе Fe, Co, Cu или Cr получено, что для пленочных систем на основе Fe и Cu в форме кривых гистерезиса наблюдается определенный перегиб, свидетельствующий о послойном перемагничивании слоев Fe, в то время как для систем на основе Fe и Cr петля гистерезиса имеет форму, подобную однослойным пленкам Fe, что говорит о преобладании ферромагнитной связи в системе. В пленочных структурах на основе Co и Cr или Cu магнитные свойства системы главным образом определяются состоянием слоев Со, поэтому форма кривых гистерезиса для обеих систем схожа с формой кривых для однослойных пленок Со, а небольшие значения коэрцитивной силы свидетельствуют о реализации ферромагнитной связи в системе. Все четыре системы характеризуются достаточно высоким значением коэффициента прямоугольности, которое при смене ориентации образца от 0 до 90° несколько уменьшается для систем Fe/Cu/Fe и Fe/Cr/Fe и, наоборот, растет в системах на основе Co и Cr. Определены величины магнитосопротивления, коэрцитивной силы, коэффициента прямоугольности и чувствительности пленочной системы к магнитному полю исследуемых пленочных систем как приборных структур для формирования первичных преобразователей. Установлена корреляция между структурно-фазовым состоянием, магнитными и магнитооптическими свойствами трехслойных пленочных систем с разным типом растворимости компонент в качестве функциональных элементов датчиков. Предложена схематическая конструкция АМР-датчика магнитного поля для трехслойных пленочных систем со спин-зависимым рассеянием электронов. В результате проведенных исследований влияния геометрии измерения, температуры термообработки и общей концентрации ферромагнитной компоненты в системе на магниторезистивные свойства определены возможные области применения пленочных систем на основе Co и Cu или Cr и Fe и Cu или Cr.The thesіs іs dedіcаted to the complex experіmentаl reseаrch between the structurаl-phаse stаte, magnetic and magnetoresistance propertіes of multіlаyer fіlm systems bаsed on the Co аnd Cu, Co аnd Cr, Fe аnd Cr, аnd Fe аnd Cu, аs the potential mаterіаls for sensіtіve elements of sensors for dіfferent purposes. Іn thіs thesis wаs found the correlаtіon between the thіckness of the mаgnetіc аnd nonmаgnetіc lаyers, the orіentаtіon of the sаmple іn аn externаl mаgnetіc fіeld, temperаture of heаt treаtment аnd mаgnetіc, mаgnetoresіstіve аnd mаgneto-optіcаl propertіes іn multіlаyer fіlm systems wіth possіble spіn-dependent scаtterіng of electrons. The vаlues of mаgnetoresіstаnce, coercіvіty, squаreness fаctor аnd sensіtіvіty of fіlm system to a mаgnetіc fіeld in the studіed fіlm systems аs devіce structures for the formаtіon of prіmаry converters were defined. The correlаtіon between the structurаl-phаse stаte, mаgnetіc аnd mаgneto-optіcаl propertіes of three-lаyer fіlm systems wіth dіfferent types of component solubіlіty аs functіonаl elements sensors was established. The schemаtіc sturucture of АMR sensor for three-lаyer fіlm systems wіth spіn-dependent scаtterіng of electrons was purposed. The possіble аreаs of аpplіcаtіons wаs іdentіfіed on the bаsіs of studіes of the effect of geometry meаsurement temperаture heаt treаtment аnd the totаl concentrаtіon of ferromаgnetіc components іn the system on the magnetic and mаgnetoresіstіve propertіes of fіlm-systems bаsed on Co аnd Cu, or Cr аnd Fe, аnd Cu or Cr

Experimental realization of on-chip topological nanoelectromechanical metamaterials

Topological mechanical metamaterials translate condensed matter phenomena, like non-reciprocity and robustness to defects, into classical platforms. At small scales, topological nanoelectromechanical metamaterials (NEMM) can enable the realization of on-chip acoustic components, like unidirectional waveguides and compact delay-lines for mobile devices. Here, we report the experimental realization of NEMM phononic topological insulators, consisting of two-dimensional arrays of free-standing silicon nitride (SiN) nanomembranes that operate at high frequencies (10-20 MHz). We experimentally demonstrate the presence of edge states, by characterizing their localization and Dirac cone-like frequency dispersion. Our topological waveguides also exhibit robustness to waveguide distortions and pseudospin-dependent transport. The suggested devices open wide opportunities to develop functional acoustic systems for high-frequency signal processing applications

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

The production of b jets in association with a Z/gamma* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The inclusive cross section for Z/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by PYTHIA.Comment: Submitted to the Journal of High Energy Physic

Search for supersymmetry in events with b-quark jets and missing transverse energy in pp collisions at 7 TeV

Results are presented from a search for physics beyond the standard model based on events with large missing transverse energy, at least three jets, and at least one, two, or three b-quark jets. The study is performed using a sample of proton-proton collision data collected at sqrt(s) = 7 TeV with the CMS detector at the LHC in 2011. The integrated luminosity of the sample is 4.98 inverse femtobarns. The observed number of events is found to be consistent with the standard model expectation, which is evaluated using control samples in the data. The results are used to constrain cross sections for the production of supersymmetric particles decaying to b-quark-enriched final states in the context of simplified model spectra.Comment: Submitted to Physical Review

Search for new physics with same-sign isolated dilepton events with jets and missing transverse energy

A search for new physics is performed in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state. The analysis is based on a data sample corresponding to an integrated luminosity of 4.98 inverse femtobarns produced in pp collisions at a center-of-mass energy of 7 TeV collected by the CMS experiment at the LHC. This constitutes a factor of 140 increase in integrated luminosity over previously published results. The observed yields agree with the standard model predictions and thus no evidence for new physics is found. The observations are used to set upper limits on possible new physics contributions and to constrain supersymmetric models. To facilitate the interpretation of the data in a broader range of new physics scenarios, information on the event selection, detector response, and efficiencies is provided.Comment: Published in Physical Review Letter

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe