Linear and quadratic magnetoelectric effect in boracite Co3B7013Br

Abstract

Linear and quadratic magnetoelectric (ME) effects have been simultaneously detected in Co-Br boracite (Co 3 B 7 o 13Br) ME coefficients a 23, a 32 and s 31 1.have be:n measured versus temperature. The results are cons1stent w1th the symmetry m'm2' down to 4 K.

Investigation of magnetic structure and phase transitions in Co311B7O13Br boracite by neutron diffraction

“…Figure 4 displays the temperature variation of the magnetic peak intensity of the first two dominant magnetic peaks {101}, {211, 301, 121, 103}. In agreement with measurements of magnetic birefringence/ magnetoelectric effect, 8 specific heat 9 and spontaneous Faraday rotation 9 a the magnetic order sets in below 17.5 K. The intensity of both peaks increases smoothly up to about T, = 10 K where its slope versus temperature begins to become steeper. This rather smooth change of slope is equally reflected in the analogous temperature dependence of the spontaneous Faraday rotation 9 a and in the change of the slope of the magnetoelectric coefficient…”

“…and from data of the magnetoelectric effect. 8 The Pc'a2 1 ' magnetic space group allows a three-dimensional canted moment arangement for the three Co sublattices (all at 4(a): x, y, z; -x, -y,! + z;!…”

“…6 • 7 • 8 b,&:. 9 •· 9 b On the basis of the magnetoelectric effect of Co--BrB and Co--I 8 • boracites the magnetic point group for both compounds was found to be m'm2' down to 4.2 K, while the Co--CI boracite undergoes two further improper structural transitions, to monoclinic point symmetry ml' (at 538 K) and trigonal3ml' (at 468 K), before it orders magnetically at 11.5 Kin the monoclinic Shubnikov group m which allows (weak) ferromagnetism.8b Specific heat measurements 9 indicate that all three compounds display a "Schottky anomaly" at temperatures lower than TN· For the Co-l compound 10 this Schottky anomaly has been interpreted on the basis of neutron diffraction results as a spin reorientation without any further change of the magnetic symmetry. It is of interest to extend this study to the other two members of the Co-X family, for which no neutron diffraction studies have previously been reported.…”

Magnetoelectric effect of Ni0.8Zn0.2Fe2O4/Sr0.5Ba0.5Nb2O6 composites

“…Table 2 Influence of sintering temperature on the particle size and density of (1 − x)Ni 0. 8 23 With the increase of ferrite phase concentration, the conduction contribution of Ni 0.8 Zn 0.2 Fe 2 O 4 phase to ε becomes more and more significant. For the sample with x = 0.7, the diffuse peak can hardly be observed at 10 kHz, and the apparent ε increases monotonically with increasing temperature and reaches to ∼12,000 at 100 • C.…”

“…The ME effect was first experimentally observed by Astrov in 1960 in Cr 2 O 3 , 6,7 and lots of monophase materials had been widely investigated during past few decades. [8][9][10] Due to the low Neel or Curie temperature and weak ME effects, it was hard to apply the monophase materials to any practical ME devices. Alternatively, bulk or laminate composites [11][12][13][14][15][16][17][18][19] of piezoelectric and magnetostrictive phases were prepared based on the concept * Corresponding author.…”