Sr₂Fe_1+xRe_1−xO₆ double perovskites: magnetoresistance and (magneto)thermopower

Abstract

Polycrystalline Sr2Fe1+xRe1−xO6 samples have been synthesized, structurally characterized by X-ray powder diffraction, transmission electron microscopy, X-ray absorption spectroscopy, and measurements of their magnetotransport properties were performed.

Thermoelectric materials taking advantage of spin entropy: lessons from chalcogenides and oxides

“…The model appears to explain the overall behaviour. On the other hand, as shown in the main panel of Figure 15 , S is hardly affected by the application of field, possibly because of the too small Zeeman energy of the field of 7 T compared to the antiferromagnetic coupling between carrier and Mn 2+ moment, of the order of θ = −100 K. This contradicting behaviour has recently also been observed in Sr 2 Fe 1+x Re 1-x O 6 double perovskites [ 54 ]. It must be emphasized that the thermopower depends on the entropy and on a transport term associated with the band structure [ 10 ].…”

n‐ to p‐type Sr2Fe1+xRe1‐xO6 double perovskites: magnetoresistance and magnetoSeebeck

“…The solid state synthesis of Sr 2 Fe 1 + x Re 1-x O 6 polycrystalline compounds with x � 0.33 was described in ref. [23] for x = 0.00, 0.25, 0.30 and 0.33. For the present study, a compound corresponding to x = 0.20 was synthesized in addition, following the same process.…”

“…[17][18] A positive MTEP has also already been observed in CuCr 1-x Ti 1 + x S 4 (x = À 0.05) at low temperature. [20] Searching for magnetic materials with a potential S(H) effect above room temperature motivated the study of double perovskites, like in Sr 2-x La x FeMoO 6 , [21] characterized by ferrimagnetic ordering temperatures far above 300 K. [22] In that respect, the lack of MTEP [23] reported for the ferrimagnetic (T C = 450 K) and magnetoresistive Sr 2 Fe 1.33 Re 0.67 O 6 double perovskite [24] was contrasting with the aforementioned previous reports on perovskite magnetic oxides. For Sr 2 Fe 1.33 Re 0.67 O 6 , the n-type electronic transport below T C is believed to be dominated by the double-exchange like mechanism between anti parallel Fe 3 + and Re 6 + magnetic spins.…”

“…For Sr 2 Fe 1.33 Re 0.67 O 6 , the n-type electronic transport below T C is believed to be dominated by the double-exchange like mechanism between anti parallel Fe 3 + and Re 6 + magnetic spins. [23] However, along the Sr 2 Fe 1 +…”

“…x Re 1-x O 6 series, as x increases from x = 0.00, the anti-site defects and the Fe/Re deviates from one, degrading the cation ordering, [25][26][27][28] as illustrated by the structural refinement for Sr 2 Fe 1.5 Re 0.5 O 6 (x = 0.5) which led to an almost completely disordered perovskite, Sr 2 (Fe 0.72 Re 0.28 ) 2b (Fe 0.78 Re 0.22 ) 2a O 6 . [23] In order to limit the influence of this disordering in the electronic and magnetic properties, we have investigated several compounds corresponding to x � 0.33 in Sr 2 Fe 1 + x Re 1-x O 6 . In the following, we report on their structural characterization, MR, thermopower (TEP) and MTEP properties.…”