Electron Spin Resonance (ESR) and Microwave Absorption Studies in TbMnO$_3$Multiferroic Compound (original) (raw)

Electron spin resonance (ESR) in multiferroic TbMnO3TbMnO3

Journal of Magnetism and Magnetic Materials, 2007

We report temperature dependent X-Band ðn$9:4 GHzÞ electron spin resonance (ESR) measurement in a single crystal of TbMnO 3 . A single Lorentzian ESR line with an isotropic g$ 1.96 was observed for TX120 K up to 600 K. The ESR signal is attributed to the Mn 3þ ions in a insulator environment. For the three crystallographic axes the temperature dependence ESR linewidth shows a strong broadening as the temperature decreases due to the presence of short range magnetic correlations. r

Magneto-optical study of the spin-polarized electronic states in multiferroic TbMnO3

Physical Review B, 2008

The magnetic and electronic properties of multiferroic TbMnO 3 in the paramagnetic, antiferromagnetic, sinusoidal, and spiral-spin phases were studied by spectral generalized magneto-optical ellipsometry. The measurements show a strong anisotropy of the dielectric tensor. A redistribution of spectral weight was observed in the diagonal components of the dielectric tensor for the temperature range from 110 to T N =46 K. In the off-diagonal elements, spectral generalized magneto-optical ellipsometry shows sensitivity to the antiferromagnetic and ferroelectric phase transitions at T N = 46 K and T F = 29 K, respectively, and a persistent signal up to 6T N .

Strong coupling between the spin polarization of Mn and Tb in multiferroic TbMnO3 determined by x-ray resonance exchange scattering

Physical Review B, 2007

We report on an x-ray resonance exchange scattering ͑XRES͒ study of multiferroic TbMnO 3 . Magnetic scattering is observed close to the Mn K edge and the Tb L III and L II edges. Surprisingly, Tb shows XRES also in the paraelectric phase, where neutron diffraction results suggested the 4f moments to be disordered. The temperature dependence of the XRES intensities shows a distinct kink close to the ferroelectric transition temperature T C for all absorption edges. We were able to model the temperature dependence for all edges, assuming a strong coupling of Mn and Tb magnetism via the spin polarized 5d conduction band. We argue that the hybridization between Mn and Tb states is a prerequisite for the multiferroic effect in this material.

Electron spin resonance (ESR) in multiferroic

Journal of Magnetism and Magnetic Materials, 2007

We report temperature dependent X-Band ðn$9:4 GHzÞ electron spin resonance (ESR) measurement in a single crystal of TbMnO 3. A single Lorentzian ESR line with an isotropic g$ 1.96 was observed for TX120 K up to 600 K. The ESR signal is attributed to the Mn 3þ ions in a insulator environment. For the three crystallographic axes the temperature dependence ESR linewidth shows a strong broadening as the temperature decreases due to the presence of short range magnetic correlations.

Nature of the Magnetic Order and Origin of Induced Ferroelectricity in TbMnO3

Physical Review Letters, 2009

The magnetic structures which endow TbMnO3 with its multiferroic properties have been reassessed on the basis of a comprehensive soft x-ray resonant scattering (XRS) study. The selectivity of XRS facilitated separation of the various contributions (Mn L2 edge, Mn 3d moments; Tb M4 edge, Tb 4f moments), while its variation with azimuth provided information on the moment direction of distinct Fourier components. When the data are combined with a detailed group theory analysis, a new picture emerges of the ferroelectric transition at 28 K. Instead of being driven by the transition from a collinear to a non-collinear magnetic structure, as has previously been supposed, it is shown to occur between two non-collinear structures.

Magnetic and Magnetoelectric Excitations in TbMnO3

Physical Review Letters, 2009

Magnetic and magnetoelectric excitations in the multiferroic TbMnO3 have been investigated at terahertz frequencies. Using different experimental geometries we can clearly separate the electroactive excitations (electromagnons) from the magneto-active modes, i.e. antiferromagnetic resonances (AFMR). Two AFMR resonances were found to coincide with electromagnons. This indicates that both excitations belong to the same mode and the electromagnons can be excited by magnetic ac-field as well. In external magnetic fields and at low temperatures distinct fine structure of the electromagnons appears. In spite of the 90 o rotation of the magnetic structure, the electromagnons are observable for electric ac-fields parallel to the a-axis only. Contrary to simple expectations, the response along the c-axis remains purely magnetic in nature.

Temperature-dependent infrared reflectivity studies of multiferroic TbMnO3: Evidence for spin-phonon coupling

Pramana-journal of Physics, 2010

We have measured near normal incidence far infrared (FIR) reflectivity spectra of a single crystal of TbMnO3 from 10K to 300K in the spectral range of 50 cm$^{-1}$ to 700 cm$^{-1}$. Fifteen transverse optic (TO) and longitudinal optic (LO) modes are identified in the imaginary part of the dielectric function epsilon_2\epsilon_2epsilon_2($\omega$) and energy loss function Im(-1/$\epsilon$($\omega$)), respectively. Some of the observed phonon modes show anomalous softening below the magnetic transition temperature T$_N$ (~ 46K). We attribute this anomalous softening to the spin-phonon coupling caused by phonon modulation of the super-exchange integral between the Mn$^{3+}$ spins. The effective charge of oxygen (Z$_O$) calculated using the measured LO-TO splitting increases below T$_N$.

Dopant-mediated structural and magnetic properties of TbMnO3

Applied Physics Letters, 2015

Structural and magnetic properties of the doped terbium manganites (Tb,A)MnO3 (A = Gd, Dy, and Ho) have been investigated using first-principles calculations and further confirmed by subsequent experimental studies. Both computational and experimental studies suggest that compared to the parent material, namely, TbMnO3 (with a magnetic moment of 9.7 μB for Tb3+) Dy- and Ho-ion substituted TbMnO3 results in an increase in the magnetic susceptibility at low fields (≤10.6μB for Dy3+ and Ho3+). The observed spiral-spin AFM order in TbMnO3 is stable with respect to the dopant substitutions, which modify the Mn-O-Mn bond angles and lead to stronger the ferromagnetic component of the magnetic moment. Given the fact that magnetic ordering in TbMnO3 causes the ferroelectricity, this is an important step in the field of the magnetically driven ferroelectricity in the class of magnetoelectric multiferroics, which traditionally have low magnetic moments due to the predominantly antiferromagneti...

Non-Resonant and Resonant X-Ray Scattering Studies on Multiferroic TbMn2O5

Physical Review Letters, 2007

Comprehensive x-ray scattering studies, including resonant scattering at Mn L-edge, Tb L-and M -edges, were performed on single crystals of TbMn2O5. X-ray intensities were observed at a forbidden Bragg position in the ferroelectric phases, in addition to the lattice and the magnetic modulation peaks. Temperature dependences of their intensities and the relation between the modulation wave vectors provide direct evidences of exchange striction induced ferroelectricity. Resonant x-ray scattering results demonstrate the presence of multiple magnetic orders by exhibiting their different temperature dependences. The commensurate-to-incommensurate phase transition around 24 K is attributed to discommensuration through phase slipping of the magnetic orders in spin frustrated geometries. We proposed that the low temperature incommensurate phase consists of the commensurate magnetic domains separated by anti-phase domain walls which reduce spontaneous polarizations abruptly at the transition. * Electronic address: kibong@postech.ac.kr † Present address: European Synchrotron Radiation Facil-