602 í Corresponding author; E-mail:hayatomonitech.ac.jp Fig. 1. Inverse magnetic susceptibilities as a function of temperature for a molar of glass composition mol of 50EuAl 2 O 4 50B 2 O 3 and 50EuAl 2 O 4 ெ10B 2 O 3 ெ40SiO 2 glasses. 602 Journal of the Ceramic Society of Japan 115 [10] 602–604 (2007) Paper j~ÖåÉíáÅ mêçéÉêíáÉë çÑ bìl–^ä O l P –_ O l P –pál O dä~ëëÉë ïáíÜ eáÖÜ bì O `çåÅÉåíê~íáçå Yousuke SUGIHARA, Tomokatsu HAYAKAWA í and Masayuki NOGAMI Department of Materials Science and Engineering, Nagoya institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466–8555 Fabrication of EuO–Al 2 O 3 –B 2 O 3 –SiO 2 glasses with high-concentration of Eu 2 ions was attempted in N 2 gas with an IR-image furnace and rapid quenching in twin rollers. Their magnetic susceptibilities of these glasses obeyed the Curie-Weiss law with the negative Curie temperature at temperatures higher than 50 K, while Eu 2 ions coupling by a superexchange-type mechanism involving oxygen ions at temperatures lower than 50 K showed a ferromagnetism. From their magnetization data at lower temperatures, we estimated an amount of Eu 2 ions in the glasses, in whose fabrication process a part of Eu 2 ions were oxidized to Eu 3 . We also measured FT–IR and Raman spectra and discussed the stable valence state of europium ions in the studied glass–matrixes. =Received June 20, 2007; Accepted August 24, 2007? Key-words : Divalent europium ions, Faraday rotation, Aluminosilicate glass, Amorphous ferromagnets, Magnetic properties 1. Introduction It is well-known that divalent Eu Eu 2 ions in glasses exhibit a large Faraday rotation in visible region. 1 Since a trivalent state of Eu ions is usually stable at ambient atmosphere, it is required for obtaining Eu 2 -containing glasses to form and quench glass-melt at reduction atmosphere or to anneal Eu 3 -doped glasses in H 2 gas at a high tempera- ture as a post-process. 2 However, such a high-temperature process in H 2 gas is always accompanied with some risks. In the present work, we used a compound containing Eu 2 ions EuAl 2 O 4 as a starting material, and attempt to fabri- cate EuO-containing glasses with high Eu 2 concentration by melting and quenching in an inert gas. To obtain a transpar- ent, glassy matrix, boron oxide B 2 O 3 and silicon dioxide SiO 2 were used as glass network-formers. Boron oxide has a low melting point ca. 450c C and is hence used to decrease a melting point of highly-EuO concentrated glass samples. Silicon dioxide is an ideal glass-network former with a good transparency and stiff framework but has a high melting point ca. 1700c C. At the present time, it is supposed that the mixture of B 2 O 3 and SiO 2 is a good selection as a network framework for high EuO concentration. Eu 3 ion has a non- magnetic ground state 7 F 0 ; total angular momentum J0 at low temperatures, which allows us to neglect the contribution from Eu 3 ions to their magnetic behaviors. Thus, we can estimate an amount of Eu 2 ions in the glasses from their magnetization data. In addition, we studied a relationship between structural properties of the glasses and the state of europium ions using FT–IR and Raman spectra. 2. Experimental The compositions of glasses obtained in this work are 50EuAl 2 O 4 ெ50B 2 O 3 EuAlB50 and 50EuAl 2 O 4 ெ10B 2 O 3 ெ 40SiO 2 EuAlB10Si40 in mol. As a starting material, a Eu 2 -compound of EuAl 2 O 4 was first synthesized in solid- state reaction with Eu 2 O 3 , C, Al 2 O 3 142 in molar at 1200c C for 10 h in Ar gas. The resultant powders were mixed with appropriate amounts of B 2 O 3 and SiO 2 , and com- pressed into molding 8 mmqj25 mm by an uniaxial com- pressor with 3 massPVA polyvinyl alcohol as a binder. The molding thus obtained was sintered by heat-treatments at 1200c C for 3 h in Ar gas for EuAlB50 and at 900c C for 3 h in N 2 gas for EuAlB10Si40, respectively. By melting them with an infraredIR-image furnace and rapid quenching in twin rollers in N 2 gas, Eu 2 ions doped glasses were successfully fabricated. EuAlB50 and EuAlB10Si40 glasses were both transparent and yellow-colored due to f–d transitions of Eu 2 ions. Magnetic properties of these glasses were estimated with a superconducting quantum interference device SQUID mag- netometer Quantum Design, MPMS at temperature-range over 10 to 300 K in 0–5 T of magnetic fields. FT-IR spectra were recorded in the 500–1800 cm 1 range with Fourier transform infrared spectrophotometer JASCO, FTIR– 460plus by a specular reflection technique. Raman spectra were recorded in the 800–1600 cm 1 range with micro-Raman spectrometer JASCO, NRS–2000. The excitation wave- length was 514 nm from Ar laser. 3. Results and discussion Figure 1 shows their inverse magnetic susceptibilities x 1 as