Dielectric and magnetic characteristics of Ca1−xMnxMoO4 (0 ≤ x ≤ 0.15) nanomaterials

Abstract

Scheelite-type Ca1−xMnxMoO4 (x = 0.0, 0.01, 0.05, 0.10 and 0.15) nanomaterials were successfully synthesized via a combustion route. Dielectric studies showed a weak n-type electrical conductivity characteristic for insulators and low relative permittivity (εr < 15) decreasing with increasing Mn2+ content. CaMoO4 and Mn2+-doped nanomaterials are chemically compatible with Al and Ag electrodes and promising for low-temperature co-fired ceramic applications. Magnetic studies showed, at room-temperature diamagnetism for pure CaMoO4, the balance between diamagnetism and paramagnetism for Ca1−xMnxMoO4 (x = 0.01) and paramagnetic behaviour when 0.05 ≤ x ≤ 0.15 as well as the short-range antiferromagnetic interactions growing in strength as Mn2+ content increases. The Landé factor fitting procedure showed a spin-only contribution to the magnetic moment. CaMoO4 matrix unexpectedly revealed the residual paramagnetism at low temperatures derived probably from the molybdenum ions having unpaired 4d electrons as well as a paramagnetic-diamagnetic transition at 70 K.

Magnetic and Electrical Characteristics of Nd3+ and Mn2+-Co-doped Calcium Molybdato-Tungstates Single Crystals

“…No intrinsic region in the relation, σ(10 3 /T), was also observed among others in Ca 1−x Mn x (MoO 4 ) 0.50 (WO 4 ) 0.50 ceramics, 13 Ca 1−x Mn x MoO 4 nanomaterials, 12 CdRE 2 W 2 O 10 tungstate mi crocrystals (RE = Y, Nd, Sm, and Gd−Er), 42 and Ca 1−3x−y Co y □ x Gd 2x (MoO 4 ) 1−3x (WO 4 ) 3x molybdato-tungstate micropowders. 14 Residual electrical conductivity of the ptype up to 230 K and the n-type above this temperature (Figure 7) in the extrinsic region seem to be related to the presence of a small amount of cationic and anion vacancies in the studied single crystals.…”

“…Band gaps determined from the band dispersion calculations indicated that both compounds are direct band gap insulators, with values of 3.41 and 4.09 eV for CaMoO 4 and CaWO 4 , respectively. 11 Our previous studies of calcium molybdate nanomaterials doped with Mn 2+ ions 12 and calcium molybdato-tungstate microcrystals doped with Mn 2+13 or Co 2+ and Gd 3+14 ones have generally shown that they are nonconductive diamagnets or paramagnetics with a spin-only contribution for molybdates and a spin−orbit coupling for molybdato-tungstates. In these materials, a relatively low value of dielectric permittivity at low frequencies was observed, which is characteristic for space charge polarization.…”

“…The R value is equal to 0.0149. In the case of the CMNMWO single crystal (x = 0.0098; y = 0.0050), the lattice constants are as follows: a = b = 5.23207 (12) and c = 11.4424(5) Å. The R value is equal to 0.0164.…”