Mathematics & Physics 2015, 8(3), 273–280 УДК 538.955 Crystal Structure and Magnetic Properties in Pyroxenes Li0.7Na0.3FeGe2O6 Tamara V.Drokina∗ German A.Petrakovskii† Kirensky Institute of Physics SB RAS Akademgorodok, 50/38, Krasnoyarsk, 660036 Russia Dmitrii A.Velikanov‡ Kirensky Institute of Physics SB RAS Akademgorodok, 50/38, Krasnoyarsk, 660036 Siberian Federal University Svobodny, 79, Krasnoyarsk, 660041 Russia Maxim S.Molokeev§ Kirensky Institute of Physics SB RAS Akademgorodok 50/38, Krasnoyarsk, 660036 Far Eastern State Transport University Serysheva, 47, Khabarovsk, 680021 Russia Elena G.Rezina¶ Siberian Federal University Svobodny, 79, Krasnoyarsk, 660041 Russia Received 05.05.2015, received in revised form 08.06.2015, accepted 02.07.2015 The Li0,7Na0,3FeGe2O6 solid solution has been synthesized by the solid-phase reaction. <...> The clinopyroxene compound has been investigated by X-ray diffraction and by bulk magnetic measurements. <...> The structural properties of the cation substitution compound are presented. <...> Using SQUID techniques the temperature dependence of the magnetic susceptibility was measured. <...> It exhibits a sharp maximum, which is suggested the phase transition from the paramagnetic state to a magnetically ordered state below 15.5 K in the sample of pyroxene solid solution. <...> All rights reserved c – 273 – Tamara V.Drokina, German A.Petrakovskii, . <...> Magnetic studies have been carried out for the family pyroxenes compound: there are various types of magnetic state (antiferromagnetic [1–4], ferromagnetic [3–5], modulated magnetic structure [6,7], spin gap state [8]) connected to the features of the pyroxene crystal structure which allows the existence of competing magnetic exchange interactions. <...> Magnetic interaction between the chains (Fe–O–Ge(Si)–O–Fe) is weakened due to the presence of non-magnetic Ge(Si)O4 tetrahedra. <...> Type of magnetic structure depends critically on the geometric topologies of the atomic structure which is determined the ratio of the intrachain (Fe-O-Fe) and interchain (Fe-O-X-O-Fe) exchange interactions parameters. <...> The room temperature crystal structure of LiFeGe2O6 is monoclinic with space group P21/c [10]. <...> The room temperature crystal structure of NaFeGe2O6 is <...>