Studia Universitatis Babeș-Bolyai Physica http://193.231.18.162/index.php/subbphysica <p><strong>ISSN (print):</strong> 0258-8730 <br /><strong>ISSN (online):</strong> 2065-9415<br /><strong>ISSN-L:</strong> 2065-9415<br /><strong>Subject: </strong>Physics Journal <br /><strong>Text in:</strong> English <br /><strong>Year of the first edition: </strong>1957<br /><strong>Print Edition History:</strong><br />1957:<em> Buletinul Universitatilor "V. Babes" si "Bolyai" Cluj. Seria Ştiintele naturii,</em> ISSN 0365-9216. 1958-1961: <em>Studia Universitatis Babes-Bolyai. Series I. Matematica, Fizica, Chimie,</em> ISSN 0578-5413. 1962-1969: S<em>tudia Universitatis Babes-Bolyai. Series Mathematica-Physica,</em> ISSN 0039-3436. 1970-1974: <em>Studia Universitatis Babes-Bolyai. Series Physica,</em> ISSN 0370-8578. <br />1975-now: <em>Studia Universitatis Babes-Bolyai. Physica,</em> ISSN 0258-8730.<br /><strong>Periodicity: </strong>half-yearly (June, December)<br /><strong>Type of the publication: </strong>scientific / academic <br /><strong>Editors: </strong>Daniel Aurelian ANDREICA, Claudiu LUNG,<br />Babeș-Bolyai University, Cluj-Napoca, Romania<br />Contact: <a href="mailto:claudiu.lung@ubbcluj.ro">claudiu.lung@ubbcluj.ro</a><br /><strong>Fully Open Access: Yes<br />Publication fees: None</strong></p> en-US claudiu.lung@ubbcluj.ro (Studia UBB Physica) studiaubb@ubbcluj.onmicrosoft.com (Alina Vesa) Fri, 30 Dec 2022 00:00:00 +0000 OJS 3.3.0.10 http://blogs.law.harvard.edu/tech/rss 60 FOREWORD: ANNIVERSARY OF PROFESSOR ROMULUS TETEAN VINTELER http://193.231.18.162/index.php/subbphysica/article/view/5661 <p>I appreciate the opportunity offered by this <em>anniversary issue</em> of the scientific journal Studia Physica to note some important aspects related to the didactic and research activity of professor doctor Romulus Tetean. Profesor Romulus Tetean was born in Sântejude, Cluj County, Romania, on November 11, 1957. He graduated the Faculty of Physics at Babeș-Bolyai University in 1981. Thanks to the <em>exceptional results</em> obtained during his undergraduate studies, Romulus Tetean was among the most <em>meritorious students</em> who attended the Solid State Physics master's degree at Babeș-Bolyai University, graduating in 1982. He pursued his PhD studies between 1993 and 1997 at the same university, under the supervision of professor Emil Burzo. This period allowed him to advance his scientific competences in the field of <em>materials science</em>, more precisely in that of the <em>magnetism of intermetallic compounds</em> of 3d transition metals with rare earths. The scientific research of prof. Tetean was mainly directed to the study of the structural, electronic, magnetic and transport properties of different <em>classes of materials</em>, such as <em>rare earth </em>- 3d transition metal intermetallic compounds, permanent magnets, nanostructured materials, perovskites and <em>superconducting materials</em> with possible technical applications such as permanent magnets, sensors, biomedicine and magnetic refrigeration. He was involved in the preparation of <em>new classes of materials</em> and characterization by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), magnetic susceptibility, magnetization, specific heat, electronic properties, Mossbauer effect, and muon spin rotation and relaxation (μSR).</p> <p> </p> Viorel POP Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5661 Fri, 30 Dec 2022 00:00:00 +0000 MAGNETOCALORIC EFFECT IN La1.2R0.2Ca1.6Mn2O7 (R=Tb, Dy, Ho, Er) PEROVSKITES SYNTHESIZED BY SOL-GEL METHOD http://193.231.18.162/index.php/subbphysica/article/view/5662 <p>Nanocrystalline double layered La<sub>1.2</sub>R<sub>0.2</sub>Ca<sub>1.6</sub>Mn<sub>2</sub>O<sub>7</sub> manganites with R = Tb, Dy, Ho, and Er were synthesized by sol-gel method. The XRD measurements indicate that all samples are <em>single phase</em> with a Sr<sub>3</sub>Ti<sub>2</sub>O<sub>7</sub>-type tetragonal (I4<em>/mmm</em>) structure and mean crystallite sizes between 22 nm and 27 nm. The magnetic measurements evidence a <em>spin-glass like behavior</em> at low temperatures for all samples, which may be due to frustration of random competing ferromagnetic and antiferromagnetic interactions together with the <em>anisotropy</em> originating from the <em>layered structure</em>. A moderate <em>magnetocaloric effect</em> was found for all samples, with the <em>maximum entropy</em> <em>change</em> located at temperatures near the magnetic transition ones, but high <em>RCP</em>(<em>S</em>) values were obtained due to the broadened <em>magnetic entropy curves</em>.</p> Roxana DUDRIC, Gabriela SOUCA, Firuța GOGA Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5662 Fri, 30 Dec 2022 00:00:00 +0000 INVESTIGATION OF THE PHYSICAL PROPERTIES OF MnNi(1-X)MX ALLOYS WHERE M=Ti, Al http://193.231.18.162/index.php/subbphysica/article/view/5664 <p>Mn<sub>50</sub>Ni<sub>50-x</sub>M<sub>x</sub>, where M= Ti, Al and x=0, 2.5, 5 and 10, alloys with the L10 <em>crystal structure</em> were successfully synthesized. The martensite type transformation was fond to be strongly affected by <em>doping</em>. Both x=10 samples show a <em>spin glass type behavior</em> while the sample doped with Al also shows large exchange bias.</p> Răzvan HIRIAN, A. MERCEA, Viorel POP Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5664 Fri, 30 Dec 2022 00:00:00 +0000 MAGNETIC PROPERTIES OF (Fe,Co)5SiB2 ALLOYS BY W DOPING http://193.231.18.162/index.php/subbphysica/article/view/5665 <p>The intrinsic <em>magnetic properties</em> (magnetic moments, magneto-crystalline anisotropy, Curie temperatures) of the Fe<sub>5-x-y</sub>Co<sub>y</sub>W<sub>x</sub>SiB<sub>2</sub> alloys have been calculated using the <em>spin-polarized relativistic</em> Korringa-Kohn-Rostoker (SPRKKR) <em>band structure method</em>. Our calculations show that for several compounds with x ≥0.5, the <em>magnetocrystalline anisotropy energy</em> (MAE) became axial. Also, theoretical calculations for Fe<sub>4</sub>WSiB<sub>2</sub> compound found a magnetization decrease (with about 20%), a <em>Curie temperature</em> decrease of about 30% but an increased axial magnetocrystalline anisotropy compared with the corresponding values for Fe<sub>5</sub>SiB<sub>2.</sub> Several Fe<sub>5-x</sub>W<sub>x</sub>SiB<sub>2 </sub>alloys (x = 0, 0.1, 0.2, 0.5, 1) have been prepared by <em>arc melting</em> of corresponding high purity elements in Ar controlled atmosphere. Composition analysis of the Fe<sub>5-x</sub>W<sub>x</sub>SiB<sub>2 </sub>alloys found an <em>impurity phase</em> along with the tetragonal <em>I4/mcm</em> phase of pure Fe<sub>5</sub>SiB<sub>2</sub>. The magnetic measurements found the decrease of the magnetization any significant increase of the <em>coercivity</em> due to W doping.</p> Răzvan HIRIAN, Viorel POP, Olivier ISNARD, Diana BENEA Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5665 Fri, 30 Dec 2022 00:00:00 +0000 CONDUCTANCE OF AN ONE AND DOUBLE-LEVEL QUANTUM DOT http://193.231.18.162/index.php/subbphysica/article/view/5666 <p>We analytically study the expression of the <em>electric charge current</em> through a two-terminal quantum dot in the linear response approximation. We analyse the one-level and the two-level <em>quantum dot scaled conductance </em>taking into account the relevant parameters. We also present the results for the conductance in the <em>Sommerfeld approximation</em>.</p> Ioan GROSU Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5666 Fri, 30 Dec 2022 00:00:00 +0000 STRUCTURE AND MORPHOLOGY OF ZnO FILMS CO-DOPED WITH AL AND RARE EARTH DEPOSITED BY SPRAY COATING TECHNIQUE http://193.231.18.162/index.php/subbphysica/article/view/5668 <p>In this work, the influence of <em>co-doping</em> with Al and rare earth ions (RE= Er, Gd, Nd) on the structure and morphology of zinc oxide (ZnO) films is presented. <em>Spray coated thin films</em> were obtained using a mixture of nitrate substances diluted in equal quantities of <em>distilled water</em> and <em>ethanol</em>. The <em>coated films</em> were deposited on quartz glass and Si(100) substrates using a constant concentration of 0.15M, a temperature of 210ºC, pressure of 2 bar and 10 minutes time of deposition. After this step, the <em>coated films</em> were annealed at 3 different <em>temperatures</em> (600ºC, 800ºC and 1000ºC) for 5 minutes each. The influence of dopant and annealing treatment upon <em>crystallographic structure</em> of the films was analyzed by X-ray diffraction (XRD). Microstructural and surface analysis from <em>scanning electron microscopy</em> (SEM) and AFM measurements evidenced that the type of doping and the annealing treatment modify the surface morphology of the films.</p> Maria-Iuliana TOMA, Daniel MARCONI, Claudiu LUNG, M. POP, Aurel POP Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5668 Fri, 30 Dec 2022 00:00:00 +0000 SUSPENSION BASED ON A MIXTURE OF TITANIA-SILICA-FUNCTIONALIZED GRAPHENE OXIDE FOR SURFACE CONSOLIDATION OF HISTORICAL ANDESITE STONE AND MORTAR http://193.231.18.162/index.php/subbphysica/article/view/5669 <p><em>Three-components suspension</em>, based on a mixture of titania (TiO<sub>2</sub>)-silica (SiO<sub>2</sub>)-functionalized graphene oxide (GO) is prepared and used for surface consolidation of <em>historical andesite</em> stone and mortar. For comparison, mono- and bi-component suspensions are also involved in this study. In order to increase the <em>attachment capacity</em> of GO to substrate with <em>silicon</em>, GO functionalized with (3-aminopropyl) triethoxysilane (GO-APTES) was involved. Unmodified and modified by painting with prepared <em>suspensions andesite</em> and mortar samples were investigated by <em>microscopy</em> (Optic and SEM-EDX), XRD, FT-IR and Raman spectra before and after 6 months of exposure to <em>ambient conditions</em>. After investigation, even the amount of used <em>consolidant suspension</em> was low, the stability of the modified samples was found that remains constant and in a long time it is possibly to reach even a higher <em>stability level</em>. This approach provides the idea that the <em>prepared suspension</em> could be an interesting option to be involved in <em>stone</em> and <em>mortar consolidation-restoration field</em>.</p> Liviu Cosmin COTEȚ, C. SĂLĂGEAN, Alin Grig MIHIȘ, István-Attila SZÉKELY, Zsejke Réka TÓTH, Lucian BAIA, Monica BAIA, Gabriela OLTEANU, Iulian Daniel OLTEANU, Virginia DANCIU Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5669 Fri, 30 Dec 2022 00:00:00 +0000 ENHANCING THE PHOTOLUMINESCENCE OF POLYFLUORENE-BASED THIN FILMS VIA ILLUMINATION http://193.231.18.162/index.php/subbphysica/article/view/5670 <p>We show in this work that exposing <em>thin films</em> of conjugated poly[9,9-bis(2-ethylhexyl)-9<em>H</em>-fluorene-2,7-diyl] to light under <em>nitrogen atmosphere</em> led to an increase of their emission up to 2.2 folds. This enhancement was due to the appearance of <em>structural changes</em> in the glassy and β-phase conformations induced upon <em>thin film illumination</em>, as revealed by the Franck-Condon analysis of the photoluminescence spectra. Interestingly, the <em>photoluminescence</em> of thin films remained at the enhanced value for 75 days after stopping the illumination, most probably due to the permanent <em>structural changes</em> induced upon <em>illumination</em>.</p> Ioan PETROVAI, Otto TODOR-BOER TODOR-BOER, Leontin DAVID, Ioan BOTIZ Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5670 Fri, 30 Dec 2022 00:00:00 +0000 RASHBA FIELD CONTRIBUTION AND ELECTRIC FIELD CONTROL OF THE MAGNETIC ANISOTROPY http://193.231.18.162/index.php/subbphysica/article/view/5671 <p>The anatomy of the <em>Perpendicular Magnetic Anisotropy</em> (PMA) in magnetic multilayered thin film heterostructures and the possibility to efficiently manipulate it by <em>external electric fields</em> represent major issues for technological applications in magnetic data storage devices. Solving a standard quantum model based on a Stoner-Rashba Hamiltonian, we illustrate that the magnetic properties in <em>ultrathin magnetic films</em> arise from the competing components identified in the magnetic energy: the Rashba correction to the Stoner splitting, a <em>pseudo-dipolar contribution</em> to the anisotropy energy proportional to the electric field at the interface that would favor <em>in-plane magnetization</em> configuration and a uniaxial-like perpendicular anisotropy term. This last term is responsible on the <em>perpendicular magnetization</em> configuration in ultrathin films and depends on the square of the <em>electric field</em> at the surface of the film. Investigating the time evolution of the magnetic system, we described the <em>macrospin magnetization dynamics</em> in terms of a Rashba field induced magnetization precession. Despite its simplicity, the quantum approach underlines the basic issues related to the physical origin and the mechanisms of the <em>perpendicular magnetization</em> in ultrathin magnetic films and illustrates the capability of manipulation by <em>external gating electric field</em>, in experiments similarly to Nuclear Magnetic Resonance.</p> Roxana-Alina ONE, Coriolan Viorel TIUȘAN Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5671 Fri, 30 Dec 2022 00:00:00 +0000 VIBRATIONAL FEATURES OF DIPHENYLHYDANTOIN http://193.231.18.162/index.php/subbphysica/article/view/5672 <p>The <em>molecular vibrations</em> of diphenylhydantoin (DPH) were investigated in crystalline sample at room temperature, by using Fourier transform <em>infrared</em> (FT-IR), FT- and conventional <em>Raman spectroscopies</em>. Furthermore, <em>density functional</em><em> theory</em> (DFT) calculations were utilized to confirm and clarify the experimental data. Two methods were evaluated for <em>accurate prediction</em> of the vibrational spectra: i) vibrational anharmonic calculations on DPH monomer based on the second-order perturbation theory; ii) harmonic calculations on a cluster of five <em>DPH molecules</em>.</p> Raluca LUCHIAN, Zsuzsanna BORSAY, Dana MANIU, Nicolae LEOPOLD, Vasile CHIŞ Copyright (c) 2022 Studia Universitatis Babeș-Bolyai Physica https://creativecommons.org/licenses/by-nc-nd/4.0 http://193.231.18.162/index.php/subbphysica/article/view/5672 Fri, 30 Dec 2022 00:00:00 +0000