Domain wall patterning and giant response functions in ferrimagnetic spinels
L. L. Kish, A. Thaler, M. Lee, A. V. Zakrzewski, D. Reig-i-Plessis, B. Wolin, X. Wang, K. C. Littrell, R. Budakian, H. D. Zhou, V. S. Zapf, A. A. Aczel, L. DeBe… 展开作者
L. L. Kish, A. Thaler, M. Lee, A. V. Zakrzewski, D. Reig-i-Plessis, B. Wolin, X. Wang, K. C. Littrell, R. Budakian, H. D. Zhou, V. S. Zapf, A. A. Aczel, L. DeBeer-Schmitt, G. J. MacDougall
The manipulation of mesoscale domain wall phenomena has emerged as a powerful strategy for designing ferroelectric responses in functional devices, but its full potential has not yet been realized in the field of magnetism. We show that mechanically strained samples of Mn$_3$O$_4$ and MnV$_2$O$_4$ exhibit a stripe-like patterning of the bulk magnetization below known magnetostructural transitions, similar to the structural domains reported in ferroelectric materials. Building off our previous magnetic force microscopy data, we use small angle neutron scattering to show that these patterns extend to the bulk, and demonstrate an ability to manipulate the domain walls via applied magnetic field and mechanical stress. We then connect these domains back to the anomalously large magnetoelastic and magnetodielectric response functions reported in these materials, directly correlating local and macroscopic measurements on the same crystals.
Large magnetocaloric effect has been observed in Mn3O4 around its ferrimagnetic transition at TN = 42.75 K. Field-induced isothermal entropy changes (\DeltaS) were derived from both magnetic and calorimetric techniques. The maximum |\DeltaS| and adiabatic temperature change (ΔTad) at TN are 11 J kg-1 K-1 and 1.9 K, respectively, for a magnetic field change of 20 kOe. Moreover, it is found that the complex magnetic phase transitions taking place below TN produce additional -but smaller- features on \DeltaS(T).
Solid solutions of nominal composition [ZnGa$_2$O$_4$]$_{1-x}$[Fe$_3$O$_4$]$_x$, of the semiconducting spinel ZnGa$_2$O$_4$ with the ferrimagnetic spinel Fe$_3$O$_4$ have been prepared with $x$ = 0.05, 0.10, and 0.15. All samples show evidence for long-range magnetic ordering with ferromagnetic hysteresis at low temperatures. Magnetization as a function of field for the $x$ = 0.15 sample is S-shaped at temperatures as high as 200 K. Mössbauer spectroscopy on the $x$ = 0.15 sample confirms the presence of Fe$^{3+}$, and spontaneous magnetization at 4.2 K. The magnetic behavior is obtained witho…
Spinel Li$_x$Mn$_2$O$_4$ is a key cathode material that is used extensively in commercial Li-ion batteries. A challenge with this material has been that the capacity of the battery fades with cycling, an effect that can be traced to the presence of an anti-ferromagnetic insulator phase in the fully lithiated LiMn$_2$O$_4$ (LMO) and the associated charge disproportionation that drives distortions of the MnO$_6$ octahedra. Here, by combining x-ray magnetic Compton scattering experiments with parallel first-principles computations, we show that the anti-ferromagnetic phase of LMO is surrounded by…
We assess the potential of the ferrimagnetic spinel ferrites CoFe2O4 and NiFe2O4 to act as spin filtering barriers in magnetic tunnel junctions. Our study is based on the electronic structure calculated by means of first-principles density functional theory within different approximations for the exchange correlation energy. We show that, in agreement with previous calculations, the densities of states suggest a lower tunneling barrier for minority spin electrons, and thus a negative spin-filter effect. However, a more detailed analysis based on the complex band-structure reveals that both sig…
We demonstrate that the onset of complex spin orders in ACr$_2$O$_4$ spinels with magnetic A$=$Co, Fe and Cu ions lowers the lattice symmetry. This is clearly indicated by the emergence of anisotropic lattice dynamics -- as evidenced by the pronounced phonon splittings -- even when experiments probing static distortions fail. We show that the crystal symmetry in the magnetic phase is reduced from tetragonal to orthorhombic for FeCr$_2$O$_4$ and CuCr$_2$O$_4$ with Jahn-Teller active A-site ions. The conical spin structure in FeCr$_2$O$_4$ is also manifested in the phonon frequencies. In contras…
Sintered samples of a spinel oxide LiFeCr4O8, where Cr3+ and Fe3+ ions have localized moments, were found to show a large magnetic-field-induced volume increase approaching 500 ppm by applying a magnetic field of 9 T. This large volume increase appeared only at around 30 K. At 30 K, a spin-reorientation transition from ferrimagnetic to conical order occurs, giving rise to this large volume increase. The coexistence of ferrimagnetic and conical phases at this transition was found to be important, suggesting that such a large magnetic-field-induced volume change can be realized at various magnet…
Unraveling the Origin of Ferrimagnetic Signatures in (Fe,Mn,Ga)2O3 Bixbyites: The Role of Structurally-Undetectable Spinel Impurities
Kirensky Institute of Physics, Federal Research Center KSC SB RAS（基连斯基物理研究所，俄罗斯科学院西伯利亚分院克拉斯诺亚尔斯克科学中心）；Siberian Federal University（西伯利亚联邦大学）；Far Eastern State Transport University（远东国立交通大学）；National Research Centre “Kurchatov Institute”（库尔恰托夫国家研究中心）；Professor V.F. Voino-Yasenetsky Krasnoyarsk State Medical University（V.F.沃伊诺-亚涅茨基克拉斯诺亚尔斯克国立医科大学）；Institute of Physics, Kazan Federal University（喀山联邦大学物理研究所）；Siberian State University of Science and Technologies（西伯利亚国立科学技术大学）；Federal Research Center "Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences"（俄罗斯科学院西伯利亚分院克拉斯诺亚尔斯克科学中心联邦研究中心）；Synchrotron Radiation Facility - Siberian Circular Photon Source "SKlF" Boreskov Institute of Catalysis of Siberian Branch of the Russian Academy of Sciences (SRF "SKIF")（俄罗斯科学院西伯利亚分院博列斯科夫催化研究所同步辐射设施——西伯利亚环形光子源“SKIF”）
We perform ultrasound velocity measurements on a single crystal of nearly-metallic spinel Co$_{1.21}$V$_{1.79}$O$_4$ which exhibits a ferrimagnetic phase transition at $T_C \sim$ 165 K. The experiments reveal a variety of elastic anomalies in not only the paramagnetic phase above $T_C$ but also the ferrimagnetic phase below $T_C$, which should be driven by the nearly-itinerant character of the orbitally-degenerate V 3$d$ electrons. In the paramagnetic phase above $T_C$, the elastic moduli exhibit elastic-mode-dependent unusual temperature variations, suggesting the existence of a dynamic spin-…
Multiferroicity in the Presence of Exchange Bias: The Case of Spinel CoMn2O4
School of Physical Science, Jawaharlal Nehru University（贾瓦哈拉尔·尼赫鲁大学物理科学学院）；Special Centre for Nanoscience, Jawaharlal Nehru University（贾瓦哈拉尔·尼赫鲁大学纳米科学特别中心）
We report high temperature synchrotron X-ray diffraction (SXRD), dc magnetization and current-voltage (I-V) characteristics for the samples of Co$_{2.75}$Fe$_{0.25}$O$_4$ ferrite. The material was prepared by chemical reaction of the Fe and Co nitrate solutions at pH = 11 and subsequent annealing at temperatures 200 0C, 500 0C and 900 0C. The measurements were performed by cycling the temperature from 300 K to high temperature (warming mode) and return back to 300 K (cooling mode). The SXRD patterns indicated a fine bi-phased cubic spinel structure in the highly Co rich spinel oxide. Magnetiza…
A systematic study using neutron diffraction and magnetic susceptibility are reported on Mn substituted ferrimagnetic inverse spinel Ti$_{1-x}$Mn$_{x}$Co$_2$O$_4$ in the temperature interval 1.6 K $\leq$ $T$ $\leq$ 300 K. Our neutron diffraction study reveals cooperative distortions of the $T$O$_6$ octahedral for all the Jahn-Teller active ions $T$ = Mn$^{3+}$, Ti$^{3+}$ and Co$^{3+}$, which are confirmed by the X-ray photoelectron spectroscopy. Two specific compositions ($x$ = 0.2 and 0.4) have been chosen because of their unique features: noncollinear Yafet-Kittel type ordering, and weak tet…
Controlling multiferroic behavior in materials will enable the development of a wide variety of technological applications. However, the exact mechanisms driving multiferroic behavior are not well understood in most materials. Two such materials are the spinels MnV2O4 and Mn3O4, where mechanical strain is thought to play a role in determining magnetic behavior. Bulk studies of MnV2O4 have yielded conflicting and inconclusive results, due in part to the presence of mesoscale magnetic inhomogeneity, which complicates the interpretation of bulk measurements. To study the sub-micron-scale magnetic…
A comparative study of the non-equilibrium magnetic phenomena (magnetic blocking, memory, exchange bias and aging effect) has been presented for ferrimagnetic Co$_{1.75}$Fe$_{1.25}$O$_4$ (CFO) and its composite with non-magnetic BaTiO$_3$ (BTO). Synchrotron X-Ray diffraction patterns have confirmed coexistence of CFO and BTO structures in composite, but magnetic spin dynamics have been remarkably modified. The blocking phenomenon of ferrimagnetic domains below the room temperature has been studied by different modes of (zero field cooled and field cooled) magnetic measurements in collaboration…
We report the magnetic properties of mechanically milled Co$_{0.2}$Zn$_{0.8}$Fe$_2$O$_4$ spinel oxide. After 24 hours milling of the bulk sample, the XRD spectra show nanostructure with average particle size $\approx$ 20 nm. The as milled sample shows an enhancement in magnetization and ordering temperature compared to the bulk sample. If the as milled sample is annealed at different temperatures for the same duration, recrystallization process occurs and approaches to the bulk structure on increasing the annealing temperatures. The magnetization of the annealed samples first increases and the…
Multiferroic particulate composites have been fabricated by taking the morphotropic phase boundary composition of ferroelectric phase Bi(Ni1/2Ti1/2)O3-PbTiO3 and magnetic phase (Ni,Zn)Fe2O4. The ferroelectric phase has coexisting monoclinic and tetragonal perovskite structures with space group Pm and P4mm, respectively whereas the magnetic phase has spinel cubic structure with space group Fd3m. Rietveld structural analysis for the each components of composite reveals that the tetragonality (c/a) of the ferroelectric phase continuously increases with increasing the concentration of magnetic pha…
Magnetoelectric materials have generated wide technological and scientific interest because of the rich phenomena these materials exhibit, including the coexistence of magnetic and ferroelectric orders, magnetodielectric behavior, and exotic hybrid excitations such as electromagnons. The multiferroic spinel material, CoCr$_2$O$_4$, is a particularly interesting example of a multiferroic material, because evidence for magnetoelectric behavior in the ferrimagnetic phase seems to conflict with traditional noncollinear-spin-driven mechanisms for inducing a macroscopic polarization. This paper repo…
