N. V. Andreeva

Low-temperature evolution of local polarization properties of PbZr0.65Ti0.35O3 thin films probed by piezoresponse force microscopy

The temperature evolution of local polarization properties in epitaxial PbZr0.65Ti0.35O3 films is studied by the low-temperature piezoresponse force microscopy (PFM). Pronounced changes in the film polarization state, including apparent polarization rotations and possible transitions between single-domain and polydomain states of individual ferroelectric nanocolumns, are revealed on cooling from the room temperature to 8 K using PFM imaging. More than two-fold increase in the coercive voltage extracted from the piezoresponse hysteresis loops is found on cooling from 240 to 8 K. The results are explained by the thermodynamic theory of strained epitaxial perovskite ferroelectric films.

Low-temperature dynamics of ferroelectric domains in PbZr0.3Ti0.7O3 epitaxial thin films studied by piezoresponse force microscopy

Dynamics of domain boundaries is expected to change drastically at low absolute temperatures but direct experimental information for this temperature range is still lacking. To clarify the mechanism of low-temperature domain dynamics, we studied the growth of ferroelectric domains in the temperature range 4.2–295 K using the out-of-plane piezoresponse mode of a cryogenic atomic force microscope (AFM). Nanoscale 180° domains were created in epitaxial PbZr0.3Ti0.7O3 films by applying short voltage pulses between the conductive AFM tip brought into contact with the bare film surface and the bottom LaSr0.7Mn0.3O3 electrode. A quantitative analysis of acquired piezoresponse images enabled us to determine the in-plane domain size as a function of the writing voltage and pulse duration. It is found that at all studied temperatures the dependence of this size on the pulse duration can be fitted by a logarithmic function, which indicates that the domain-wall velocity exponentially depends on the driving electric f...

Domain structures and correlated out-of-plane and in-plane polarization reorientations in Pb(Zr0.96Ti0.04)O3 single crystal via piezoresponse force microscopy

Pb(Zr1-xTix)O3 single crystal with a low titanium content (x = 4%) was studied by the piezoresponse force microscopy (PFM) and X-ray diffraction (XRD). The XRD studies showed that the crystal faces are orthogonal to the principal cubic axes and confirmed the existence of an intermediate phase between the high-temperature paraelectric (PE) phase and the low-temperature antiferroelectric (AFE) one. A significant temperature hysteresis of phase transitions was observed by the XRD: On heating, the AFE state transforms into the intermediate one at about 373 K and the PE phase appears at 508 K, whereas on cooling the intermediate phase forms at 503 K and persists down to at least 313 K. The PFM investigation was focused on the intermediate phase and involved measurements of both out-of-plane and in-plane electromechanical responses of the (001)-oriented crystal face. The PFM images revealed the presence of polarization patterns switchable by an applied electric field, which confirms the ferroelectric character ...

Low Temperature Ferroelectric and Magnetic Properties of Doped Multiferroic Tb0.95Bi0.05MnO3

Multiferroics are very promising materials for application in RF/microwave electronic devices. Electrical tuning of magnetism due to strong magnetoelectric coupling in these materials gives an opportunity to use them in reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). Tb0.95Bi0.05MnO3 (TMNO) multiferroic is a solid solution of TbMnO3 and BiMnO3, the interest to investigation of this nanocomposite material is caused by the possibility to obtain the multiferroic with close temperatures of magnetic and ferroelectric ordering which are higher than in pure TbMnO3. Results of TMNO crystal investigations obtained using cryogenic magnetic force and piezopresponse force microscopy techniques are presented. An existence of ferroelectric and ferromagnetic ordering in TMNO at low temperatures was observed.

Temperature Dependence of Ferroelectric Properties of the Potassium Lithium Tantalate K1−xLixTaO3 Obtained with Piezoresponse Force Microscopy Technique

Abstract In the present paper we report the first results of the study of the polar state of the surface structure of single crystal of potassium tantalate doped with Li + ions (KLT-3%) by the piezoresponse force microscopy technique in the temperature range 10–295 K. The results obtained demonstrate the existence of polar nanoregions on the surface of the KLT-3% single crystal at temperatures 10 – 80 K. Spatial distribution and temperature evolution of these polar nanoregions are analyzed. Observation of the structure of polar nanoregions of KLT-3% crystal in zero field heating after zero field cooling regime gives the evidence of the existence of spontaneous polarization in the low-temperature phase.

Atomic force microscopy with interferometric method for detection of the cantilever displacement and its application for low-temperature studies

ABSTRACT Specific features of the atomic force microscopes (AFM) with interferometric method of the cantilever displacement detections are considered in aspects of their applications for low temperature measurements in contact regimes. Brief comparison of interferometric detection with other methods of the cantilever displacement measurements is provided. A developed approach of Youngs modulus determination for AFM with interferometric cantilever-detection system is presented. Experimental results obtained on the temperature dependence of elastic properties of the AFM cantilever are used for explanation of a weak temperature dependence of the ferroelectric domain dynamics in thin ferroelectric films, previously observed by piezoresponse force microscopy.

SEM and AFM studies of two-phase magnetic alkali borosilicate glasses

The morphology and composition of four types of two-phase alkali borosilicate glasses with magnetic atoms prepared by inductive melting have been studied. The results of scanning electron microscopy point to uniform distribution of Na, Si, and O atoms in these samples while magnetic iron atoms form ball-shaped agglomerates. The magnetic properties of these agglomerates have been confirmed by magnetic force microscopy. Atomic force microscopy had shown that in these samples two different morphological structures, drop-like and dendrite net, are formed. The formation of dendrite-like structure is a necessary condition for production of porous magnetic glasses. The obtained results allow us to optimize the melting and heat treatment processes leading to production of porous alkali borosilicate glasses with magnetic properties. The first results for nanocomposite materials on the basis of magnetic glasses containing the embedded ferroelectrics KH2PO4 demonstrate the effect of applied magnetic field on the ferroelectric phase transition.

Writing Ferroelectric Nanodomains in PZT Thin Film at Low Temperatures

Thin ferroelectric films are prospective materials for applications in the area of tunable microwave electronics as a base for varactors, phase shifters, delay lines, tunable filters and antennas. The most important technological aspect of using thin polar films in electronics is a possibility of miniaturization. By means of piezoresponse force microscopy technique, it is possible to create nanometer-sized areas (or ferroelectric domains) in thin films with preferable direction of polarization. Besides the fact that these domains could be used as a bit for mass storage application, it was found, that domain walls have their own properties, moreover, they are mobile. This circumstance could give rise to a new type of technology where mobile domain walls will be the “active ingredient” of the device.

Influence of a Poling Procedure on Dynamics of Ferroelectric Domains in Thin PbZr0.3Ti0.7O3 Film at Low Temperatures

An experimental study of low temperature domain dynamics could provide information on a mechanism of domain wall motion at low temperatures in thin ferroelectric films. For this purpose we use a piezoresponse force microscopy (PFM) technique and investigate the 1800 ferroelectric domains growth in the temperature range 5 K – 295 K. Domains were created by applying a dc voltage pulses between an atomic force microscopy (AFM) tip and a bottom electrode of a thin epitaxial PbZr0.3Ti0.7O3 film. Two different types of tips were used, a semiconducting tip with dopant conductivity and a tip with metallic coating to clarify an influence of poling procedure on the domain dynamics. Created domains were then visualized and their in-plane sizes were measured with out-of-plane PFM. Dependences of lateral domain size on the duration and amplitude of dc voltage pulse were obtained. Received experimental dependences were then fitted with logarithmic function with good accuracy. This circumstance indicates on the thermally activated mechanism of domain growth and formation. Temperature dynamics of the 1800 ferroelectric domains growth does not depend on the AFM tip used in a poling procedure what allows us to conclude that the voltage transfer to the ferroelectric film does not significantly depend on the tip-film local contact properties.

Temperature Dependence of Surface Polar State of SrTiO3 Ceramics Obtained by Piezoresponse Force Microscopy

The existence of polar state on the surface of strontium titanate ceramics was obtained by piezoresponse force microscopy (PFM) in temperature range from 8 to 295 K. This polar state is nonswitchable and relaxes fast at room temperature. This fact is attributed to charge injection from tip, which provoked the formation of oxygen vacancies in subsurface layer. Low temperature dynamics of surface piezoresponse reveals an increasing of PFM contrast at 110–130 K, associated with surface structural phase transition. Temperature dependence of the average level of piezoresponse signal exhibits two peaks due to bulk structural phase transition and coherent quantum state.