Terahertz lattice dynamics of the potassium rare-earth binary molybdates

Abstract

We report a systematic study of low-energy lattice vibrations in the layered systems KY(MoO), KDy(MoO), KEr(MoO), and KTm(MoO). A layered crystal structure and low symmetry of the local environment of the rare-earth ion cause the appearance of vibrational and electronic excitations in Terahertz frequencies. The interaction between these excitations leads to sophisticated dynamical properties, including non-linear effects in paramagnetic resonance spectra. The THz study in magnetic field allows for the clear distinction between lattice vibrations and electronic excitations. We measured the THz transmission spectra and show that the low energy lattice vibrations in binary molybdates can be well described within the quasi-one-dimensional model. The developed model describes the measured far-infrared spectra, and results of our calculations agree with previous Raman and ultrasound studies.

Massive Magnetostriction of the Paramagnetic Insulator KEr(MoO4)2via a Single‐Ion Effect

“…[32] In orthorombic crystals, using the lowest order of the 4f-ion angular momentum Table 1. Measured [24,25,36] and calculated energies of the splitting of the 4 I 15/2 multiplet relative to the ground state at μ 0 H = 0 T. The corresponding wavefunctions are shown in operator, the coupling between the Er 3+ ions and the crystal lattice is described via the magnetoelastic Hamiltonian: [13,33,34]…”

“…(Stevens operators and their coefficients) [35] : dictate the splitting of the 4 I 15/2 multiplet which has been studied previously by means of optical [24] and far-infrared [25,36] spectroscopy. The results of these measurements are summarized in the top row of Table 1.…”

Crystal structures and comparisons of potassium rare-earth molybdates KRE(MoO4)2 (RE = Tb, Dy, Ho, Er, Yb, and Lu)

“…Rare-earth (RE) molybdates have been studied extensively because of their luminescent, magnetoelectric, and ferroelectric properties (Borchardt & Bierstedt, 1967;Axe et al, 1971;Pratap et al, 1987;Ponomarev et al, 1994;Shi et al, 1996;Kut'ko, 2005;Wang et al, 2007;Ponomarev & Zhukov, 2012). The RE molybdates of ARE(MoO 4 ) 2 (A = Li, Na, K, Rb, Cs, Ag) generally crystallize with the tetragonal I4 1 /a space group with the scheelite (CaWO 4 ) structure or the orthorhombic Pbcn space group (Wanklyn & Wondre, 1978;Hanuza & Fomitsev, 1980;Leask et al, 1981;Hanuza et al, 1994;Stedman et al, 1994;Shi et al, 1996;Voron'ko et al, 2004;Kut'ko, 2005;Wang et al, 2007;Mat'aš et al, 2010;Poperezhai et al, 2017). The ARE(MoO 4 ) 2 compounds having the I4 1 /a space group have luminescent properties with high thermal and hydrolytic stability (Stedman et al, 1994;Shi et al, 1996;Voron'ko et al, 2004;Wang et al, 2007) whereas the compounds with the Pbcn space group are known for the structural phase transition by the Jahn-Teller effect (Kut'ko, 2005;Mat'aš et al, 2010;Kamenskyi et al, 2014;Poperezhai et al, 2017).…”

“…The RE molybdates of ARE(MoO 4 ) 2 (A = Li, Na, K, Rb, Cs, Ag) generally crystallize with the tetragonal I4 1 /a space group with the scheelite (CaWO 4 ) structure or the orthorhombic Pbcn space group (Wanklyn & Wondre, 1978;Hanuza & Fomitsev, 1980;Leask et al, 1981;Hanuza et al, 1994;Stedman et al, 1994;Shi et al, 1996;Voron'ko et al, 2004;Kut'ko, 2005;Wang et al, 2007;Mat'aš et al, 2010;Poperezhai et al, 2017). The ARE(MoO 4 ) 2 compounds having the I4 1 /a space group have luminescent properties with high thermal and hydrolytic stability (Stedman et al, 1994;Shi et al, 1996;Voron'ko et al, 2004;Wang et al, 2007) whereas the compounds with the Pbcn space group are known for the structural phase transition by the Jahn-Teller effect (Kut'ko, 2005;Mat'aš et al, 2010;Kamenskyi et al, 2014;Poperezhai et al, 2017). Other wellknown RE molybdates RE 2 (MoO 4 ) 3 (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) crystallize with different space groups including P2 1 /c, C2/c, or P2m depending on the RE cations and the synthesis conditions (Brixner et al, 1979;Jeitschko, 1973;Ponomarev & Zhukov, 2012;Pratap et al, 1987); these phases exhibit magnetoelectric and ferroelectric properties (Borchardt & Bierstedt, 1967;Axe et al, 1971;Ponomarev et al, 1994;Ponomarev & Zhukov, 2012).…”

Grain boundaries guided vibration wave propagation in polycrystalline graphene

“…5,6 Since the mass of graphene is very small, the quality factor (QF) of the sensors to pressure and stress is remarkably high, it can be used to detect single molecular, highlighting potential applications in healthcare, homeland security and other critical elds. [7][8][9][10][11] The improved nanofabrication techniques have undoubtedly accelerated the development. 12 Kim et al has developed a exible hydrogen sensor with Pd thickness of 3 nm exhibits a gas response of $33% when exposed to 1000 ppm H 2 and it is able to detect as low as 20 ppm H 2 at room temperature (22 C).…”