Room Temperature Ferrimagnetism and Ferroelectricity in Strained, Thin Films of BiFe _0.5 Mn _0.5 O ₃

Choi, Eun-Mi,Fix, Thomas,Kursumovic, Ahmed,Kinane, Christy J,Arena, Darí,o,Sahonta, Suman-Lata,Bi, Zhenxing,Xiong, Jie,Yan, Li,Lee, Jun-Sik,Wang, Haiyan,Langridge, Sean,Kim, Young-Min,Borisevich John WileySons, Ltd 2014 Advanced Functional Materials Vol.24 No.47

<P>Highly strained films of BiFe<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>3</SUB> (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (<I>T<SUB>C</SUB></I> ∼ 600K), with a room temperature saturation moment (<I>M<SUB>S</SUB></I>) of up to 90 emu/cc (∼ 0.58 <I>μ<SUB>B</SUB></I>/f.u) on high quality (001) SrTiO<SUB>3</SUB>. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe<SUP>3+</SUP> and Mn<SUP>3+</SUP>. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.</P>

Characteristic of Hyperfine Magnesioferrite Particles Possessing Shape Anisotropy

Yim, Going,Yim, Chai-Suck 배재대학교 공학연구소 2005 공학논문집 Vol.7 No.1

The ferrimagnetic resonance technique, with the inclusion of shape anisotropy effects, was used to obtain information about the early stages in the precipitation of magnesium ferrite from iron-doped magnesia. The very small magnesioferrite particles were produced by precipitation method from solid solution of iron ion in single crystal magnesia. The temperature dependence of the resonance anisotropy field for a coherent assembly of hyperfine magnesium ferrite precipitates was investigated in the range 100~400K. The results are interpreted in terms of the shape anisotropy of the precipitates.

Nontrivial Ferrimagnetism of the Heisenberg Model on the Union Jack Strip Lattice

Tokuro Shimokawa,Hiroki Nakano 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3

We study the ground-state properties of the S = 1/2 antiferromagnetic Heisenberg model onthe Union Jack strip lattice by using the exact-diagonalization and density matrix renormalizationgroup methods. We confirm a region of a magnetization state intermediate between the N´eel-likespin liquid state and the conventional ferrimagnetic state of a Lieb-Mattis type. In the intermediatestate, we find that the spontaneous magnetization changes gradually with respect to the strength ofthe inner interaction. In addition, the local magnetization clearly shows an incommensurate modulationwith long-distance periodicity in the intermediate magnetization state. These characteristicbehaviors lead to the conclusion that the intermediate magnetization state is a non-Lieb-Mattisferrimagnetic one. We also discuss the relationship between the ground-state properties of theS = 1/2 antiferromagnetic Heisenberg model on the original Union Jack lattice and those on ourstrip lattice.

Enhanced Ferrimagnetism in Zn½Fe½Cr₂S₄

김철성,Sung Hwan Bae,김삼진 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

We have synthesized Zn½Fe½Cr₂S₄ and studied it by using with X-ray diffraction, magnetic susceptibility and Mossbauer spectroscopy measurements. The crystal structure was found to be a cubic spinel with space group Fd3m by using a Rietveld refinement of X-ray diffraction data. The lattice constant of Zn½Fe½Cr₂S₄ was determined to be a0 = 9.992 Å. The magnetization curves followed a Curie-Weiss law, with a positive θcw = 107 ± 1 K showing a ferrimagnetic behavior. The Neel temperature (TN) of Zn½Fe½Cr₂S₄ was determined to be 105 K. The Mossbauer spectra of Zn½Fe½Cr₂S₄ were obtained at various temperatures ranging from 4.2 to 300 K. The magnetic anomaly observed below TN is caused by a weakening of the spin-orbit coupling. The isomer shift value of the sample at room temperature was 0.65 mm/s, which means that the charge state of the Fe ions was ferrous in character. We have synthesized Zn½Fe½Cr₂S₄ and studied it by using with X-ray diffraction, magnetic susceptibility and Mossbauer spectroscopy measurements. The crystal structure was found to be a cubic spinel with space group Fd3m by using a Rietveld refinement of X-ray diffraction data. The lattice constant of Zn½Fe½Cr₂S₄ was determined to be a0 = 9.992 Å. The magnetization curves followed a Curie-Weiss law, with a positive θcw = 107 ± 1 K showing a ferrimagnetic behavior. The Neel temperature (TN) of Zn½Fe½Cr₂S₄ was determined to be 105 K. The Mossbauer spectra of Zn½Fe½Cr₂S₄ were obtained at various temperatures ranging from 4.2 to 300 K. The magnetic anomaly observed below TN is caused by a weakening of the spin-orbit coupling. The isomer shift value of the sample at room temperature was 0.65 mm/s, which means that the charge state of the Fe ions was ferrous in character.

Synthesis, microstructure, and magnetic properties of monosized Mn _<i>x</i> Zn _<i>y</i> Fe _{3 − <i>x</i> − <i>y</i>} O ₄ ferrite nanocrystals

Yoon, Hayoung,Lee, Ji Sung,Min, Ji Hyun,Wu, JunHua,Kim, Young Keun Springer 2013 Nanoscale research letters Vol.8 No.1

<P>We report the synthesis and characterization of ferrite nanocrystals which exhibit high crystallinity and narrow size distributions. The three types of samples including Zn ferrite, Mn ferrite, and Mn-Zn ferrite were prepared via a non-aqueous nanoemulsion method. The structural, chemical, and magnetic properties of the nanocrystals are analyzed by transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and physical property measurement system. The characterization indicates that the three types of ferrite nanocrystals were successfully produced, which show well-behaved magnetic properties, ferrimagnetism at 5 K and superparamagnetism at 300 K, respectively. In addition, the magnetization value of the ferrites increases with the increasing concentration of Mn.</P>

Exotic Magnetism of s-electron Cluster Arrays: Ferromagnetism, Ferrimagnetism and Antiferromagnetism

Takehito Nakano,Duong Thi Hanh,Yasuo Nozue,Nguyen Hoang Nam,Truong Cong Duan,Shingo Araki 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3

Alkali metal nanoclusters can be stabilized in the regular cages of zeolite crystals by the loading ofguest alkali metals. Cages are connected by the sharing of windows of the framework, and arrayed insimple cubic, diamond and body centered cubic structures in zeolites A, X and sodalite, respectively. The s-electrons have the localized nature of nanoclusters with magnetic moments, and have mutualinteractions through the windows of cages. They show exotic magnetism depending on the structuretype of zeolites, the kind of alkali metals and the average loading density of alkali atoms per cage. In zeolite A, potassium clusters are formed in α-cages that have an inside diameter of 11 °A. Theyexhibit ferromagnetic properties explained by the canted antiferromagnetism of the Mott insulator,where the 1p-like degenerate orbitals of clusters play an essential role in the magnetic properties. Na-K alloy clusters generated at supercages and β-cages of low-silica X (LSX) zeolite exhibit N´eel’sN-type ferrimagnetism at specific loading densities of alkali metals. Alkali metal clusters in sodaliteshow the ideal Heisenberg antiferromagnetism of the Mott insulator.

CoMn₂O₄ 스피넬 박막의 합성과 후열처리가 박막의 물리적 특성에 미치는 영향

김두리(D. R. Kim),김진경(J. K. Kim),윤세원(S. W. Yoon),송종현(J. H. Song) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.5

We grew spinel structured CoMn₂O₄ thin films and have studied post-growth annealing effects on their physical properties. After post-growth annealing at 700℃ that is lower than the growth temperature (720℃), crystal structure became cleared accompanying a change of surface structure. In the temperature dependences of magnetization, phase transitions were observed at ~100 K for both before and after post-growth treated samples which were not observed for the bulk. For both samples, ferromagnetic behaviors were observed above 100 K while it turned to ferrimagnetism at low temperature below 100 K. In particular, the ferrimagnetic behavior became strong after the post-growth treatment. These results indicate that the post-growth annealing process plays an important role in determining the physical properties of spinel CoMn₂O₄ thin film.

Structural and magnetic properties of bulk and thin films of Mg0.95Mn0.05Fe2O4

샤런드라쿠마르,S.K. Sharma,Alimuddin,이찬규,B.H. Koo,M. Knobel,R.J. Choudhary,Ravi Kumar 한국물리학회 2009 Current Applied Physics Vol.9 No.5

We present here a comparative study on structural and magnetic properties of bulk and thin films of Mg0.95Mn0.05Fe2O4 ferrite deposited on two different substrates using X-ray diffraction (XRD) and dc magnetization measurements. XRD pattern indicates that the bulk sample and their thin films exhibit a polycrystalline single phase cubic spinel structure. It is found that the film deposited on indium tin oxide coated glass (ITO) substrate has smaller grain size than the film deposited on platinum coated silicon (Pt–Si) substrate. Study of magnetization hysteresis loop measurements infer that the bulk sample of Mg0.95Mn0.05Fe2O4 and its thin film deposited on Pt–Si substrate shows a well-defined hysteresis loop at room temperature, which reflects its ferrimagnetic behavior. However, the film deposited on ITO does not show any hysteresis, which reflects its superparamagnetic behavior at room temperature.

Structural and magnetic properties of bulk and thin films of Mg_0.95Mn_0.05Fe₂O₄

Kumar, Shalendra,Sharma, S.K.,Alimuddin, S.K.,Knobel, M.,Choudhary, R.J.,Lee, Chan Gyu,Koo, B.H.,Kumar, Ravi Elsevier 2009 Current Applied Physics Vol.9 No.5

<P><B>Abstract</B></P><P>We present here a comparative study on structural and magnetic properties of bulk and thin films of Mg<SUB>0.95</SUB>Mn<SUB>0.05</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB> ferrite deposited on two different substrates using X-ray diffraction (XRD) and dc magnetization measurements. XRD pattern indicates that the bulk sample and their thin films exhibit a polycrystalline single phase cubic spinel structure. It is found that the film deposited on indium tin oxide coated glass (ITO) substrate has smaller grain size than the film deposited on platinum coated silicon (Pt–Si) substrate. Study of magnetization hysteresis loop measurements infer that the bulk sample of Mg<SUB>0.95</SUB>Mn<SUB>0.05</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB> and its thin film deposited on Pt–Si substrate shows a well-defined hysteresis loop at room temperature, which reflects its ferrimagnetic behavior. However, the film deposited on ITO does not show any hysteresis, which reflects its superparamagnetic behavior at room temperature.</P>

Multiferroic Properties and Local Structure of Spinel (Co,Mn)3O4

구태영,Dae-Su Lee,강선희,김일원,송종현 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.2

A room-temperature structural phase diagram for the spinel Co3−xMnxO4 (0 x 3) solidsolution system was examined to study the cubic-tetragonal phase transition. The temperaturedependentmagnetization was measured to identify the ferrimagnetic ordering at temperatures belowTC An enhanced magneto-capacitance effect was observed around TC without any appreciablehysteretic behavior due to a variation in the applied magnetic field. The directional averagedcomplex atomic form factors of both the Co and the Mn ions at two different crystallographic sitesof the oxide spinel structure near the K-absorption edges were extracted from the measured X-rayabsorption spectra. Energy dispersive atomic form factors can be used to analyze X-ray diffractiondata near the absorption edges to explore the detailed features coming from the local environmentaleffects