Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D60: Multiferroics IIFocus Recordings Available
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Sponsoring Units: DMP Chair: Manfred Fiebig, ETH Zurich Room: Hyatt Regency Hotel -DuSable C |
Monday, March 14, 2022 3:00PM - 3:36PM |
D60.00001: self-assembled multiferroic mesostructures Invited Speaker: Judith L Driscoll
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Monday, March 14, 2022 3:36PM - 3:48PM |
D60.00002: Low energy-low temperature THz excitations in RFeO3 (R=La, Pr, Er, Lu) Néstor E Massa, Karsten Holldack, Thomas Lohmiller, Leire Del Campo, Vinh Ta Phuoc, Paula Kayser, José A Alonso We report on low temperature-low energy absorptions of antiferromagnetic and ferromagnetic magnons at ~31.4 and ~26.7 cm-1 in Γ4 (Gx, Ay, Fz )-LaFeO3 with degeneracy lifted linearly by an applied field up to 7 T. In addition to these modes, in LuFeO3 ligand distortions induced by Lu 4f14 smaller radius trigger subtle changes at the perovskite B site, allowing THz Fe3+ Zeeman -split electronic crystal field (CF) ground state 6A1(S) transitions at ~10.4 cm-1. This local non-centrosymmetric departure is also found in ErFeO3 (Kramers 4f11 Er3+ ; Γ2 (Fx, Cy, Gz)<TSR ~93 K), but now with the Fe3+ Zeeman branching strongly biased by the 3d-4f exchange toward higher energies. At 5 K, there is no field induced band split but a 13-fold increase in the resonance antiferro/ferro intensity ratio. It is also remarkable the CF applied field-dependent population, matching balance between Fe3+ lower and higher Zeeman -split levels. Some Er3+ ground state transitions coincide with phonon frequencies, suggesting strong spin-phonon interactions. Antiferro and ferro resonances turn much broader when non-Kramers Pr3+, containing two unpaired 4f2 electrons, introduces ligand changes at the A site leading the antiferro mode and the lowest Pr3+ CF transition into near degeneracy. They merge into a single broad unresolved feature at 7 T. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D60.00003: Molecular beam epitaxy and ultraviolet Raman spectroscopy of hexagonal ScFeO3 films Dmitri A Tenne, Nicholas A Parker, Airin H Eddins-Schmidt, Caleb Burwell-Miller, Matthew R Barone, Darrell G Schlom Hexagonal ScFeO3 films synthesized by molecular beam epitaxy on (0001) oriented Al2O3 substrates were studied by variable temperature ultraviolet Raman spectroscopy. Films of varied thickness (10–150 nm) were grown in a monolayer controlled method by shuttering the MBE fluxes as well as by a co-deposition method so that the properties of the resulting films could be compared. The films were characterized by x-ray diffraction as well as atomic force microscopy. ScFeO3 in the hexagonal phase (isostructural to YMnO3 and other rare-earth ferrites) is predicted to be multiferroic near room temperature. This multiferroicity is a combination of ferroelectricity and antiferromagnetic order often seen in the family of rare-earth ferrites, but at significantly high temperatures in hexagonal ScFeO3. The Raman spectra of hexagonal ScFeO3 at room temperature are indicative of the polar hexagonal P63cm structure, in agreement with the x-ray diffraction spectra of the films, which are consistent with hexagonal ScFeO3. The temperature evolution of the Raman spectra of hexagonal ScFeO3 films over the range of 10-1450 K indicates a transition to a non-polar (likely P63/mmc) phase; fitting the integrated Raman intensities as a function of temperature yields a transition temperature of 950 K ± 50 K. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D60.00004: Manipulation of spin orientation via ferroelectric switching in Fe-doped Bi2WO6 from first principles Nabaraj Pokhrel, Katherine Inzani, Elizabeth A Nowadnick, Sinead M Griffin, Nima Leclerc, Sriram Poyyapakkam Ramkumar, Zachary Clemens Electric field control of single spins can probe the fundamental limits of multiferroic behavior and magnetoelectric coupling. One possible platform to explore this scenario is to form isolated spin centers in ferroelectric materials via inclusion of dilute concentrations of magnetic dopants. We investigate single spin manipulation using the Aurivillius phase ferroelectric oxide Bi2WO6 as a host. We propose that the low-symmetry environment provided by the layered crystal structure can enable control of the magnetic dopant spin-axis. Using a combination of density functional theory and group theoretic analysis, we enumerate and explore the intrinsic ferroelectric switching pathways in undoped Bi2WO6 and find that a two-step pathway has the lowest energy barrier. Then substituting a Fe3+ dopant onto one W site in a Bi2WO6 supercell, we explore how the magnetocrystalline anisotropy energy and preferred spin orientation evolve throughout ferroelectric switching. We find that the Fe3+ spin aligns along a spin-easy axis and that a 90o switch of the polarization direction leads to a 90o reorientation of the spin-easy axis. This work advances our understanding of electric field control of single spins, which has potential implications in the fields of spintronics and quantum computing. |
Monday, March 14, 2022 4:12PM - 4:24PM Withdrawn |
D60.00005: Freestanding ferroelectric bubble domains Sergei Prokhorenko, Saidur R Bakaul, Qi Zhang, Yousra Nahas, Yushi Hu, Amanda K Petford-Long, Laurent Bellaiche, Nagarajan Valanoor Particle-like bubble domains typically form in ultra-thin ferroelectrics epitaxially clamped on flat substrates. Here, using first-principle-based simulations and local PFM measurements, we inquire if they can be as well sustained in free-standing films, which will be highly promising for some technologies. We demonstrate that these non-trivial dipolar patterns can indeed be retained in a freestanding state in ferroelectric membranes, despite the presence of inhomogeneously distributed structural ripples. We further shed some light on the origin of these latter structural ripples and analyze the stability as well as special features of free-standing polar bubbles. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D60.00006: Observation of a multiferroic domain wall in a non-multiferroic environment Yannik Zemp, Mads C Weber, Ehsan Hassanpour, Lukas Kürten, Yusuke Tokunaga, Yasujiro Taguchi, Yoshinori Tokura, Thomas Lottermoser, Manfred Fiebig Ferroic domain walls, the boundaries between regions of different order-parameter orientation, exhibit properties that often differ strongly from those of the surrounding bulk material. These differences include transport, chemical or crystallographic properties. However, not much is known about the ferroic properties inside the domain walls. Cases like non-ferroic domain walls between ferroic domains or vice versa can be imagined. Here, we present the extreme case of a multiferroic domain wall in a non-multiferroic environment in Dy0.7Tb0.3FeO3 (DTFO). Using the combination of Faraday rotation and optical second harmonic generation microscopy, respectively, we show that a net-magnetization and electric polarization are present only inside the wall only, whereas the interior of the domains is neither magnetized nor polarized. By spatial deconvolution of the Faraday- and SHG signal, we determine the width of our multiferroic domain wall to be 1.25 µm with both techniques. Magnetic and electric fields can switch the magnetization and polarization inside the wall, a defining property of ferroic states, and they are also capable of expanding the multiferroic domain wall into a multiferroic bulk domain. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D60.00007: Collective Effects on the Spin-Crossover Energy Angel M Albavera Mata, Sijin Ren, Richard G Hennig, Samuel B Trickey Spin-crossover complexes are potentially important for application in memory devices and molecular switches. Probed experimentally in condensed phases, the underlying physics is a molecular low-high spin energy difference. Computations on a single molecule therefore are common [Chem. Rev. 121, 9927 (2021)]. Calculation of magnetic properties of transition-metal complexes, however, also is known to be sensitive to diverse computational choices that affect description of the spin states, structure, and magnetism [Eur. J. Inorg. Chem. 2014, 4573 (2014)]. From calculations on a set of first-row transition metal complexes using generalized and meta-generalized gradient density functionals [Phys. Rev. Lett. 77, 3865 (1996); J. Phys. Chem. Lett. 11, 8208 (2020)], we discuss the influence of collective effects on energetic differences between results obtained using condensed aggregates and isolated molecules. We find the condensed-phase collective effects can account for differences by as much as 10% of the molecular value, affecting the predictions of spin-crossover transition temperatures. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D60.00008: Temperature Dependent Conductance Measurements of Co Spin Crossover Molecules Jared Phillips, Saeed Yazdani, Wyatt Highland, Thilini K Ekanayaka, Ping Wang, Michael Shatruk, Ruihua Cheng, Peter A Dowben Spin crossover (SCO) complexes are functional materials that can be switched between a low spin and a high spin state by an external stimulus. They are a promising candidate for a wide range of applications, including molecular-based switches, sensors and memory devices. Accompanying the change in spin states, there is often an observed change in the conductance as well, which makes SCO molecules attractive for organic molecular-based spintronics. In this work we will present a systematic study of temperature dependent conductance measurements for two types of SCO molecules, [Co(SQ)(Cat)(4-CN-py)2] and [Co(SQ)(Cat)(3-tpp)2]. The thin film samples were prepared on interdigitated devices with electrodes separated by 5 µm, using different solvents in an effort to study the solvent effects. The conductance change induced by light and electric field stimulation was also studied. We noticed that the electric conductance shows intriguing properties near the transition temperature and this could be due to the switching of spin states through an electric field. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D60.00009: Control of ferromagnetic properties by spontaneous polarization of various perovskite substrates ABO3: First principles study Dameul Jeong, Young-Kyun Kwon As the size of CMOS-based semiconductor devices decreases, various quantum mechanical limitations become serious issues to be solved. To overcome limitations, spin-based devices have been proposed. However, there are several issues in spin-based devices as well. Compared to the energy required to maintain the magnetic information, it needs 105 times higher energy to switch spin states. Recently, spin-based devices demonstrated that the ferromagnetic spin states can be switched by a multiferroic material with much lower switching energy than conventional CMOS devices by a factor of 10 to 30. More recently, instead of this multiferroic material, a soft magnetic cladding structure was proposed for ferromagnetic switching. Still, the key issue is how to lower magnetic anisotropy energy enabling easier spin switching. Using first-principles density functional theory, we investigate the magnetic properties of a ferromagnetic layer, such as Fe, stacked on various ferroelectric oxides ABO3 where A is one of the alkaline earth metals (Ca, Sr, or Ba) and B is a transition metal in the titanium group (Ti, Zr, or Hf). We explore how to utilize spontaneous polarization of ferroelectric substrates to tailor the magnetic properties including magnetic anisotropy of the ferromagnetic layer. |
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