Properties of K2NiF4-Type Oxides Sr2FeO∼4
Properties of K2NiF4-Type Oxides Sr2FeO∼4
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K2NiF4型氧化物Sr2FeO〜4的性质
DOI：
10.1006/jssc.1994.1043
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发表时间：
1994
影响因子：
5.4
通讯作者：
P. Adler
中科院分区：
文献类型：
--
作者：
P. Adler
在流动的O2气氛中，从金属氧化物中制备了含四价铁的K2NIF4型氧化物Sr2FeO4的微缺氧样品，并对样品的电阻率、磁化率和穆斯堡尔效应进行了研究。Sr2FeO-∼-4是一种Mott型反铁磁半导体，其尼尔温度T_N约为60K，T_N以上的穆斯堡尔谱由一对Fe4+四极子组成，其同质异能移δ为-0.017 mm/s~(-1)。磁有序相的穆斯堡尔谱显示至少有四个Fe4+超精细六重态，这是与相变有关的局部结构扭曲的证据。一些半导体钙钛矿型铁氧酸盐(IV)在TN以上和TN以下都没有观察到按照2Fe4+→Fe3++Fe5+的电荷歧化。从8K穆斯堡尔谱得到的磁场BHf在25~33T范围内，这表明四价铁具有形式的d4高自旋组态和共价Fe-O键。与文献报道的钙钛矿型SrFeO3和K2NiF4型相(A，A‘)2M0.5Fe0.5O4(A=Ca，Sr，Ba，A’=La，M=Mg，Zn，Li)的性质进行了比较.
Abstract Slightly oxygen deficient samples of the K 2 NiF 4 -type oxide Sr 2 FeO 4 with tetravalent iron have been prepared from the metal oxides in flowing O 2 gas atmosphere and investigated by resistivity, magnetic susceptibility, and Mossbauer effect measurements. Sr 2 FeO ∼4 is a Mott-type antiferromagnetic semiconductor with a Neel temperature T N of about 60 K. The Mossbauer spectra above T N consist of a single Fe 4+ quadrupole doublet with an isomer shift δ of -0.017 mm sec -1 . The Mossbauer spectra of the magnetically ordered phase reveal at least four Fe 4+ hyperfine sextets which are evidence for local structural distortions associated with the phase transition. A charge disproportionation according to 2 Fe 4+ → Fe 3+ + Fe 5+ which was found previously for some semiconducting perovskite-type oxoferrates(IV) was neither observed above nor below T N . The magnetic hyperfine fields B hf derived from the Mossbauer spectra at 8 K range from 25 to 33 T which suggests a formal d 4 high spin configuration with covalent Fe-O bonding for the tetravalent iron. The properties of Sr 2 FeO 4 are compared with literature data of the perovskite SrFeO 3 and the K 2 NiF 4 -type phases ( A, A′ ) 2 M 0.5 Fe 0.5 O 4 ( A = Ca, Sr, Ba, A′ = La, and M = Mg, Zn, Li).