Low-frequency magnetic sensing by magnetoelectric metglas/bidomain LiNbO3 long bars

We present an investigation into the magnetic sensing performance of magnetoelectric bilayered metglas / bidomain LiNbO3 long thin bars operating in a cantilever or free vibrating regime and under quasi-static and low-frequency resonant conditions. Bidomain single crystals of Y+128o-cut LiNbO3 were engineered by an improved diffusion annealing technique with a polarization macrodomain structure of the “head-to-head” and “tail-to-tail” type. Long composite bars with lengths of 30, 40 and 45 mm, as well as with and without attached small tip proof masses, were studied. ME coefficients as large as 550 V/cm∙Oe, corresponding to a conversion ratio of 27.5 V/Oe, were obtained under resonance conditions at frequencies of the order of 100 Hz in magnetic bias fields as low as 2 Oe. Equivalent magnetic noise spectral densities down to 120 pT/Hz1/2 at 10 Hz and to 68 pT/Hz1/2 at a resonance frequency as low as 81 Hz were obtained for the 45 mm long cantilever bar with a tip proof mass of 1.2 g. In the same composite without any added mass the magnetic noise was shown to be as low as 37 pT/Hz1/2 at a resonance frequency of 244 Hz and 1.2 pT/Hz1/2 at 1335 Hz in a fixed cantilever and free vibrating regimes, respectively. A simple unidimensional dynamic model predicted the possibility to drop the low-frequency magnetic noise by more than one order of magnitude in case all the extrinsic noise sources are suppressed, especially those related to external vibrations, and the thickness ratio of the magnetic-to-piezoelectric phases is optimized. Thus, we have shown that such systems might find use in simple and sensitive room-temperature low-frequency magnetic sensors, e.g., for biomedical applications.publishe

Magnetic Properties of the Densely Packed Ultra-Long Ni Nanowires Encapsulated in Alumina Membrane

High-quality and compact arrays of Ni nanowires with a high ratio (up to 700) were obtained by DC electrochemical deposition into porous anodic alumina membranes with a distance between pores equal to 105 nm. The nanowire arrays were examined using scanning electron microscopy, X-ray diffraction analysis and vibration magnetometry at 300 K and 4.2 K. Microscopic and X-ray diffraction results showed that Ni nanowires are homogeneous, with smooth walls and mostly single-crystalline materials with a 220-oriented growth direction. The magnetic properties of the samples (coercivity and squareness) depend more on the length of the nanowires and the packing factor (the volume fraction of the nanowires in the membrane). It is shown that the dipolar interaction changes the demagnetizing field during a reversal magnetization of the Ni nanowires, and the general effective field of magnetostatic uniaxial shape anisotropy. The effect of magnetostatic interaction between ultra-long nanowires (with an aspect ratio of >500) in samples with a packing factor of ≥37% leads to a reversal magnetization state, in which a “curling”-type model of nanowire behavior is realized. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: An.T. (Andrei Turutin) acknowledges the financial support of the Russian Science Foundation (Grant No. 19-79-30062) in part of the experimental work. A.K. (Alexander Kislyuk) and I.K. (Ilya Kubasov) acknowledge the financial support of the Ministry of Science and Higher Education of the Russian Federation as a part of the State Assignment (basic research, Project No. 0718-2020-0031 “New magnetoelectric composite materials based on oxide ferroelectrics having an ordered domain structure: production and properties”) in part of the XRD study

Magnetoelectric metglas/bidomain y + 140°-cut lithium niobate composite for sensing fT magnetic fields

We investigated the magnetoelectric properties of a new laminate composite material based on y+140°-cut congruent lithium niobate piezoelectric plates with an antiparallel polarized “head-to-head” bidomain structure and metglas used as a magnetostrictive layer. A series of bidomain lithium niobate crystals were prepared by annealing under conditions of Li2O outdiffusion from LiNbO3 with a resultant growth of an inversion domain. The measured quasi-static magnetoelectric coupling coefficient achieved |αE31| = 1.9 V·(cm·Oe)–1. At a bending resonance frequency of 6862 Hz, we found a giant |αE31| value up to 1704 V·(cm·Oe)–1. Furthermore, the equivalent magnetic noise spectral density of the investigated composite material was only 92 fT/Hz1/2, a record value for such a low operation frequency. The magnetic-field detection limit of the laminated composite was found to be as low as 200 fT in direct measurements without any additional shielding from external noises.publishe

Magnetic Properties of the Densely Packed Ultra-Long Ni Nanowires Encapsulated in Alumina Membrane

High-quality and compact arrays of Ni nanowires with a high ratio (up to 700) were obtained by DC electrochemical deposition into porous anodic alumina membranes with a distance between pores equal to 105 nm. The nanowire arrays were examined using scanning electron microscopy, X-ray diffraction analysis and vibration magnetometry at 300 K and 4.2 K. Microscopic and X-ray diffraction results showed that Ni nanowires are homogeneous, with smooth walls and mostly single-crystalline materials with a 220-oriented growth direction. The magnetic properties of the samples (coercivity and squareness) depend more on the length of the nanowires and the packing factor (the volume fraction of the nanowires in the membrane). It is shown that the dipolar interaction changes the demagnetizing field during a reversal magnetization of the Ni nanowires, and the general effective field of magnetostatic uniaxial shape anisotropy. The effect of magnetostatic interaction between ultra-long nanowires (with an aspect ratio of >500) in samples with a packing factor of ≥37% leads to a reversal magnetization state, in which a “curling”-type model of nanowire behavior is realized. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: An.T. (Andrei Turutin) acknowledges the financial support of the Russian Science Foundation (Grant No. 19-79-30062) in part of the experimental work. A.K. (Alexander Kislyuk) and I.K. (Ilya Kubasov) acknowledge the financial support of the Ministry of Science and Higher Education of the Russian Federation as a part of the State Assignment (basic research, Project No. 0718-2020-0031 “New magnetoelectric composite materials based on oxide ferroelectrics having an ordered domain structure: production and properties”) in part of the XRD study

Piezoelectric Actuation of Graphene-Coated Polar Structures

Ferroelectric materials based on lead zirconate titanate (PZT) are widely used as sensors and actuators because of their strong piezoelectric activity. However, their application is limited because of the high processing temperature, brittleness, lack of conformal deposition, and a limited possibility to be integrated with the microelectromechanical systems (MEMS). Recent studies on the piezoelectricity in the 2-D materials have demonstrated their potential in these applications, essentially due to their flexibility and integrability with the MEMS. In this work, we deposited a few layer graphene (FLG) on the amorphous oxidized Si3N4 membranes and studied their piezoelectric response by sensitive laser interferometry and rigorous finite-element modeling (FEM) analysis. Modal analysis by FEM and comparison with the experimental results show that the driving force for the piezoelectric-like response can be a polar interface layer formed between the residual oxygen in Si3N4 and the FLG. The response was about 14 nm/V at resonance and could be further enhanced by adjusting the geometry of the device. These phenomena are fully consistent with the earlier piezoresponse force microscopy (PFM) observations of the piezoelectricity of the graphene on SiO2 and open up an avenue for using graphene-coated structures in the MEMS. © 1986-2012 IEEE.This work was supported in part by the Russian Foundation or Fundamental Research under Grant 16-29-14050, in part by the Ministry of Education and Science of the Russian Federation in the framework of the Increase Competitiveness Program of MISiS under Grant K2-2019-015, in part by the Project CICECO-Aveiro Institute of Materials financed by national funds through the Portuguese Foundation for Science and Technology/MCTES under Grants UIDB/50011/2020 and UIDP/50011/2020, and in part by the Center for Nanophase Materials Sciences, which is a Department of Energy Office of Science User Facility. The work was also supported by Government of the Russian Federation (Act 211, Agreement 02.A03.21.0006) and by the Ministry of Science and Higher Education of the Russian Federation (state task FEUZ-2020-0054). The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. The work of Yakov Kopelevich was supported in part by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and in part by the Fundação de Amparo à Pesquisa do Estado de S. Paulo (FAPESP) (Brazil)

Magnetic Properties of the Densely Packed Ultra-Long Ni Nanowires Encapsulated in Alumina Membrane

High-quality and compact arrays of Ni nanowires with a high ratio (up to 700) were obtained by DC electrochemical deposition into porous anodic alumina membranes with a distance between pores equal to 105 nm. The nanowire arrays were examined using scanning electron microscopy, X-ray diffraction analysis and vibration magnetometry at 300 K and 4.2 K. Microscopic and X-ray diffraction results showed that Ni nanowires are homogeneous, with smooth walls and mostly single-crystalline materials with a 220-oriented growth direction. The magnetic properties of the samples (coercivity and squareness) depend more on the length of the nanowires and the packing factor (the volume fraction of the nanowires in the membrane). It is shown that the dipolar interaction changes the demagnetizing field during a reversal magnetization of the Ni nanowires, and the general effective field of magnetostatic uniaxial shape anisotropy. The effect of magnetostatic interaction between ultra-long nanowires (with an aspect ratio of >500) in samples with a packing factor of ≥37% leads to a reversal magnetization state, in which a “curling”-type model of nanowire behavior is realized

Бидоменные сегнетоэлектрические кристаллы: свойства и перспективы применения

Lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) are among the most important and most widely used materials of coherent and nonlinear optics, as well as acoustics. High degree of uniformity and reproducibility has become the foundation of technology for manufacturing high-quality crystals, absorbed by many suppliers around the world. However, the above areas do not limit the use of LiNbO3 and LiTaO3 due to their unique piezoelectric and ferroelectric properties. One promising application of crystals is the design of electromechanical transducers for precision sensors and actuators. In this respect, the high thermal stability of the piezoelectric and mechanical properties, the lack of hysteresis and creep make it possible to create electromechanical converters with wide operating temperature range, that is beyond the capability of commonly used ferroelectric ceramics. The main advantage of LiNbO3 and LiTaO3 over other single-crystal piezoelectrics is ferroelectric domain structure regulation toward targeted impact on the device characteristics. One of the most striking examples of electromechanical transducer design through domain engineering is the formation of a so-called bidomain ferroelectric structure in crystal. It represents a single-crystalline plate with two macrodomains with opposite directions of spontaneous polarization vectors separated by a charged domain wall. High switching fields make inversion domains stable at temperatures up to 1000 °C. This review summarizes the main achievements in the formation of bidomain structure and near surface inversion domains in LiNbO3 and LiTaO3 crystals. We present the domain structure virtualization methods in crystals and non-destructive methods for controlling the domain boundary position. The report contains a comparative analysis of the methods for forming inversion domains in crystals, and the patterns and technological control methods of the domain structure are discussed. The basic physical models have been proposed in the literature to explain the effect of the inversion domains formation. In the present paper we outline what one sees as strengths and weaknesses of these models. The strategies of crystallographic cut selection to create devices based on bidomain crystals are briefly discussed. We provide examples of the implementation of devices based on bidomain crystals such as actuators, sensors, acoustic transducers, and waste energy collection systems.Ниобат лития (LiNbO3) и танталат лития (LiTaO3) относятся к важнейшим и наиболее широко применяемым материалам когерентной и нелинейной оптики, а также акустики. Высокие требования, предъявляемые к однородности и воспроизводимости характеристик, стали основой для создания промышленной технологии выпуска высококачественных кристаллов, освоенной многими предприятиями мира. Однако использование LiNbO3 и LiTaO3 не ограничивается перечисленными выше областями техники благодаря выраженным пьезо- и сегнетоэлектрическим свойствам. Одним из перспективных направлений использования кристаллов является создание на их основе электромеханических преобразователей для прецизионных сенсоров и актюаторов. При этом высокая термическая стабильность пьезоэлектрических и механических свойств, отсутствие гистерезиса и крипа позволяют создавать электромеханические преобразователи, способные работать в широком диапазоне температур, недостижимом для обычно используемых для этих целей сегнетокерамических материалов. Главным преимуществом LiNbO3 и LiTaO3 перед другими монокристаллическими пьезоэлектриками является возможность направленного воздействия на характеристики устройств путем управления сегнетоэлектрической доменной структурой кристаллов. Одним из наиболее ярких примеров использования доменной инженерии для создания электромеханических преобразователей на основе кристаллов является формирование в них так называемой бидоменной структуры — двух доменов макроскопического размера, расположенных в одной кристаллической пластине, имеющих встречно направленные векторы спонтанной поляризации и разделенных заряженной доменной стенкой. Высокие коэрцитивные поля переключения делают инверсные домены стабильными вплоть до температуры Кюри (порядка 1140 °C у LiNbO3 и 600 °C у LiTaO3). В обзоре рассмотрены основные достижения в области формирования бидоменной структуры и приповерхностных инверсных доменов в кристаллах LiNbO3 и LiTaO3. Представлены методы визуализации доменной структуры в кристаллах и неразрушающие методы контроля положения междоменной границы. Проведен сравнительный анализ методов формирования инверсных доменов в кристаллах, обсуждены закономерности и технологические приемы управления доменной структурой. Приведены основные физические модели, предложенные в литературе для объяснения эффекта образования инверсных доменов, рассмотрены их сильные и слабые стороны. Кратко перечислены способы выбора кристаллографического среза для создания устройств, в которых используются бидоменные кристаллы. Приведены примеры реализации устройств на основе бидоменных кристаллов: актюаторов, сенсоров, акустических преобразователей, систем сбора бросовой энергии

Анализ диффузионных профилей фосфора в легированном галлием германии методом координатно-зависимой диффузии

The phosphorus concentration profiles in germanium in In0,01Ga0,99As/In0,56Ga0,44P/Ge heterostructures with gallium co-diffusion, that were obtained during first cascade of a multicascade solar cell formation were analyzed. The diffusion of phosphorus took place from the layer In0,56Ga0,44P together with the diffusion of gallium in a strongly gallium-doped germanium substrate, which determined the features of the diffusion process. First of all, co-diffusion of gallium and phosphorus leads to formation of two p—n junctions. Fick’s laws cannot be used for diffusion description. Distribution of the P diffusivity (DP) in the depth of the sample was determined by two methods —Boltzmann—Matano (version of Sauer—Freise) and the coordinate-dependent diffusion method. It is shown that when we have used the coordinate-dependent diffusion method, the DP values are more consistent with the known literature data due to taking into account the drift component of diffusion. The tendency of DP to increase at the heterostructure boundary and to decrease at approaching to the main p—n junction is observed for both calculation methods. DP increase in the near-surface region of the p—n-junction, whose field is directed to the interface of the heterostructure, and the decrease in the region of the main p-n junction, whose field is directed in the opposite direction, as well as the observed growth of DP with the electron concentration, leads to the conclusion that diffusion in this case takes place as the part of negatively charged VGeP complexes, as in the case of P diffusion alone.В связи с развитием технологии многокаскадных солнечных элементов (МК СЭ) возрос интерес к германию как к подложке и материалу первого каскада МК СЭ на основе соединений АIIIВV. Фосфор и галлий являются основными легирующими элементами в германии, поэтому интерес к процессам их диффузии проявлялся с момента начала разработок технологии изготовления p—n-переходов в германии. Дан анализ профилей распределения фосфора в германии в структуре In0,01Ga0,99As/In0,56Ga0,44P/Ge в условиях содиффузии с галлием, полученные при формировании первого каскада МК СЭ. Диффузия фосфора проходила из слоя In0,56Ga0,44P вместе с диффузией галлия в сильно легированную галлием подложку германия, что определило особенности процесса диффузии. В первую очередь совместная диффузия галлия и фосфора приводит к формированию не одного, а двух p—n-переходов. Диффузионные профили фосфора не могут быть описаны законами Фика. Распределение коэффициента диффузии фосфора DP по глубине образца определяли двумя методами: Больцмана—Матано в варианте Зауэра—Фрейзе и методом координатно-зависимой диффузии. Показано, что учет дрейфовой компоненты в методе координатно-зависимой диффузии дает значения DP, более соответствующие известным литературным данным. Тенденция увеличения DP у границы гетероструктуры и уменьшения при приближении к основному переходу наблюдается для обоих методов расчета. Поле приповерхностного p—n-перехода, направлено к границе раздела гетероструктуры, а поле основного p—n-перехода — в противоположную сторону, также, как и наблюдаемый рост DP с концентрацией электронов. Увеличение DP в области приповерхностного p—n-перехода и уменьшение в области основного p—n-перехода позволяют сделать вывод, что диффузия в гетероструктуре идет в составе отрицательно заряженных комплексов VGeP, как и в случае диффузии одного компонента

Формирование стабильных индуцированных доменов в области заряженной междоменной границы в ниобате лития с помощью зондовой микроскопии

The influence of a charged domain wall on the formation of the induced domain structures in congruent x-cut lithium niobate crystals (LiNbO3) is studied. By diffusion annealing in air ambient near Curie temperature, as well as infrared annealing in oxygen-free ambient bi- and multidomain ferroelectric structures containing charged domain walls «head-to-head» and «tail-to-tail» were formed. By Kelvin probe mode of atomic force microscopy (AFM) surface potential near the charged domain walls was investigated. We studied surface needle-shaped induced microdomains which were formed in a vicinity of the domain boundary and far from it by applying of voltage to the cantilever being in a contact with the surface of the sample. Dependence of morphology of the induced domain structure on the crystal’s electric conductivity was demonstrated. Screening effect of charged «head-to-head» domain wall on a shape and size of the domain, that was induced near the boundary is shown. We described partition of the single needle-shaped domains formed by AFM cantilever to several microdomains having a shape of several beams based in a common nucleation point. We found an influence of the charged domain wall on the topography of the samples, which consisted in the appearance of a long groove corresponding to the domain boundary after the reducing annealing.Сегнетоэлектрические кристаллы ниобата лития (LiNbO3) c искусственно сформированной доменной структурой находят широкое применение в оптических системах генерации кратных гармоник лазерного излучения, акустооптике, прецизионных актюаторах, датчиках вибрации и магнитного поля, в том числе предназначенных для применения при повышенных температурах, в перспективе — в запоминающих устройствах ЭВМ. Исследовано влияние заряженной междоменной границы на формирование индуцированных доменных структур в конгруэнтных кристаллах ниобата лития (LiNbO3) неполярного x-среза. Методами диффузионного отжига на воздухе вблизи температуры Кюри и инфракрасного отжига в бескислородной среде в образцах были сформированы би- и полидоменные сегнетоэлектрические структуры, содержащие заряженные доменные границы типа «голова-к-голове» и «хвост-к-хвосту». В режиме Кельвин-моды атомно-силового микроскопа (АСМ) исследован поверхностный потенциал в окрестности заряженной междоменной границы. Исследованы приповерхностные клиновидные индуцированные микродомены, сформированные в области заряженной междоменной границы и вдали от нее путем приложения электрического потенциала на кантилевер АСМ, находящийся в контакте с поверхностью кристалла. Продемонстрирована зависимость морфологии индуцированной доменной структуры от электропроводности кристаллов. Показано экранирующее действие заряженной междоменной границы типа «голова-к-голове» на форму и размер домена, индуцированного в непосредственной близости к доменной стенке. Описано разбиение одиночных клиновидных доменов, образующихся при локальной переполяризации кристаллов восстановленного ниобата лития с помощью кантилевера АСМ, на семейства микродоменов, имеющих форму сонаправленных лучей, выходящих из общего центра зарождения. Обнаружено влияние заряженной междоменной границы на топографию образцов, заключающееся в возникновении при восстановительном отжиге протяженного углубления, совпадающего с линией заряженной границы