Neutron diffraction study on the two-dimensional Ising systemKEr(MoO4)2

Abstract

The magnetic properties of the two-dimensional Ising antiferromagnet KEr͑MoO 4 ͒ 2 have been investigated below and above transition temperature T N ϳ 0.95 K in zero field and in fields up to 6.5 T by means of elastic neutron-diffraction, heat-capacity, and magnetization measurements. The low-temperature signal recorded at 0.34 K by neutron diffraction is explained within a noncollinear magnetic structure model. However, additional contribution is also present when applying the external magnetic field along the c axis even at temperatures well above the magnetic transition temperature T N . Various explanations are discussed.

Magnetic-Field Induced Slow Relaxation in the Ising-Like Quasi-One-Dimensional Ferromagnet KEr(MoO_4)_2

“…The compound is a magnetic insulator with a layered crystal structure and crystallizes in the orthorhombic space group P bcn (D 14 2h ) [6]. The first coordination sphere of Er 3+ consists of eight oxygen atoms forming a slightly distorted square antiprism.…”

“…Previous studies revealed anomalous behavior of isothermal magnetization at temperatures between 2 and 3 K in the field applied along the c-axis [6]. At higher temperatures the anomaly vanished, while at lower temperatures, the anomaly developed to a well defined plateau between 0.5 and 1 T [7].…”

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).…”

Giant reversible rotating cryomagnetocaloric effect inKEr(MoO4)2induced by a crystal-field anisotropy

“…The ground state of a free Er 3+ is 4 I 15/2 multiplet, which is split into eight Kramers doublets with the energies E/k B = 22, 46, 107, 266, 372, 456, and 467 K above the ground doublet [17]. Electron paramagnetic resonance spectra [18] and isothermal magnetization [19] measured above 2 K revealed a strong anisotropy of a ground doublet characterized by anisotropic g-factor values 19, 2, and 0.7, measured along the easy, medium, and hard magnetization axis, respectively. Relatively weak spin-phonon coupling influences the position of the first excited doublet due to interaction of the electronic state with the transverse acoustic vibration modes.…”