Low-temperature anomalous magnetic behavior of Co2TiO4 and Co2SnO4

Abstract

We report the low-temperature anomalous magnetic behavior of ferrimagnetic spinels cobalt orthotitanate (Co2TiO4), which exhibits magnetic compensation behavior across 31.74 K, and cobalt orthostannate (Co2SnO4) exhibiting two sequential magnetic transitions, namely (i) ferrimagnetic to paramagnetic transition with Néel temperature TN ∼ 41 K and reentrant spin-glass behavior with glass transition temperature TSG ∼ 39 K. The Arrott plot (H/M versus M2) criterion has been used to extricate the order of sequential magnetic transitions occurring below TN. Negative slopes of the Arrott plots below 32 K, metamagnetic-like character of the M-H isotherms, anomalies in the specific-heat (CP T−1 versus T) below 15 K, and a zero-crossover of isothermal magnetic-entropy-change (ΔS) signify the presence of pseudo first-order discontinuous magnetic phase transition in the low-temperature regime 5 K ≤ T ≤ 32 K. The dc- and ac-susceptibilities of both Co2TiO4 and Co2SnO4 are interpreted in terms of frozen-spin-clusters, which are responsible for very large magnitudes of the coercivity HC ∼ 20 kOe and bipolar-exchange bias HEB ∼ −20 kOe observed below 10 K.

Structural, magnetic and dielectric properties of the novel magnetic spinel compounds ZnCoSnO4 and ZnCoTiO4

“…Therefore, both compounds may enter into a glassy spin state just below TN, which had been observed previously in Co2SnO4 11,18,19 .…”

“…which may well be a result of the diluted Co 2+ magnetism by Zn 2+ substitution. Figure 4 further indicates a separation of the ZFC and FC curves below TN, which is reminiscent of a glassy spin magnetic moment commonly observed in (anti)ferromagnetic and ferrimagnetic spinels 11,[15][16][17] . The Figure 4 insets demonstrate that the deviations between ZFC and FC curves (maxima in the ZFC curves) occur at temperatures very close to the Neel transitions TN as indicated by the maxima in the differentiated FC curves, for both ZnCoSnO4 and ZnCoTiO4.…”

“…In the work presented here, isovalent Co 2+ magnetic doping of Zn2SnO4 and Zn2TiO4 by substitution of Zn 2+ was studied in order to modify the optical absorption properties and increase the functionality of the material by adding a magnetic component to it. The end member spinel compounds Co2SnO4 and Co2TiO4 exhibit ferrimagnetic moments below TN = 41 K and TN = 48 K respectively 11,12 , which arise from the different magnetic moments of Co 2+ on tetrahedral or octahedral sites. From an alternative point of view it may be regarded that the Co 2+ magnetism in the ferrimagnetic spinels Co2SnO4 and Co2TiO4 was diluted by partial Zn 2+ substitution.…”

Relaxor behavior and electrothermal properties of Sn- and Nb-modified (Ba,Ca)TiO3 Pb-free ferroelectric

“…2(c)], which indicates transition from PNRs at higher temperatures to ferroelectric domains below T m . Nevertheless, the rather weak and broad nature of the peak for excess specific heat point to the lack of establishment of a true long-range order [44]. Piezoresponse force microscopy corroborates the findings above as only nanoscale domains can be observed at RT (see Fig.…”

Electric and magnetic properties of titanium-cobalt-oxide single crystals produced by floating zone melting with light heating

“…The cobalt titanates Co 2 TiO 4 , CoTiO 3 , and CoTi 2 O 5 are a promising class of materials with many possible applications among others as new magnetodielectric materials. Lately a noticeable increase of interest for investigations of magnetic, electrical, optical properties of various Co-containing oxide compounds occurs [1][2][3][4]. But the most of physical investigations of cobalt titanates were carried out using of polycrystals or thin films.…”