Effect of Pressure on Magnetic Properties of Hexacyanochromates

Abstract

We present the study of pressure effect on magnetic properties of TM 2+ 3 [Cr III (CN) 6 ] 2 · nH 2 O ferrimagnets and ferromagnets (TM = Cr and Co) under pressures up to 0.9 GPa. Applied pressure strengthens super--exchange interaction in Cr 2+ -prussian blue analogues with dominant antiferromagnetic interaction JAF leading to increase in the Curie temperature TC (∆T c /∆p = 29.0 K/GPa) and reduces T C of Co 2+ -prussian blue analogues with dominant ferromagnetic interaction JF (∆Tc/∆p = −1.8 K/GPa). The rise of J AF interaction is attributed to the enhanced value of the single electron overlapping integral S. On the other hand, the applied pressure slightly affects bonding angles between magnetic ions mediated by the cyano-bridge and reduces the strength of magnetic coupling. Changes of the magnetization curve with pressure can be attributed to changes of magnetic anisotropy. The reduction of magnetization with pressure observed on Cr 2+ -prussian blue analogues can be explained by pressure induced transition from Cr 2+ high spin state to Cr 2+ low spin state. All pressure induced changes are reversible.

The Effect of Pressure on Magnetic Properties of KMnCr(CN)6.

“…The remnant magnetization μ r and coercive field H c for this material are close to zero [4]. As can be seen from Fig.…”

“…K which is placed into an interstitial sites; A is 3d metal which occupies all the summits and all the centres of the faces and the [B(CN) 6 ] are located at the octahedral sites. One-third of [B(CN) 6 ] vacancies are filled by M -an alkali metal cation; the B coordination sphere is left unchanged but the mean coordination sphere of A becomes A(NC) 4 (H 2 O) 2 [1]. A metal ion is placed next to nitrogen atom and thus due to weak ligand field is almost always high spin.…”

“…Magnetic properties of PBAs are very sensitive to the effect of external parameters such as humidity, light and pressure [1,2]. For PBAs the effect of pressure triggered the following mechanisms: high spinlow spin transition [4] or magnetic pole inversion [5] can be induced by pressure. The first work dealing with the study of pressure effect on magnetic properties was referred by Awaga et.…”

The Effect of Pressure on Magnetic Properties of Prussian Blue Analogues

“…This simple model mentioned above has already been tested on the TM 2+ 3 [Cr III (CN) 6 ] 2 •zH 2 O and KM 2+ [Cr(CN) 6 ] systems, where TM 2+ = Cr 2+ , Mn 2+ , Ni 2+ , Co 2+ , and M 2+ = Mn 2+ , Ni 2+ [29][30][31][32][33][34][35][36][37][38][39][40]. Our paper is focused on the pressure effect on crystal structure and magnetic properties.…”

“…The above-mentioned magnetic model was tested on the TM +2 3[Cr III (CN)6]2•zH2O system [29][30][31][32][33][34][35][36][37][38] and KTM 2+ Cr(CN)6 [39,40], where TM 2+ is a 3d ion and the following papers [29,32,34,[38][39][40] are focused on the pressure effect on magnetic properties of these two types of PBs. The Cr III in the low spin anion [Cr III (CN)6] 3− has (t2g) 3 orbital resulting in six ferromagnetic (FM) and nine antiferromagnetic (AFM) pathways, with (t2g) 3 (eg) 2 orbitals of Mn 2+ leading to JAF interaction.…”