content_image/366763.jpg content_image/366764.jpg content_image/366760.jpg content_image/366762.jpg content_image/366761.jpg content_image/366759.jpg content_image/366758.jpg
<img src='content_image/366763.jpg'>

and 

where l$_{i}$ = m$_{a,i}$ − m$_{b,i}$ and m$_{i}$ = m$_{a,i}$ + m$_{b,i}$ . The frequencies ω$_{a}$ = γKM$_{s}$ , ω$_{ex}$ = γλM$_{s}$ , ω$_{me}$ = γαP$_{o}$M$_{s}$ and ω$_{o}$ = γH$_{o}$ are associated with the magnetic anisotropy, exchange, magnetoelectric coupling and the external magnetic field respectively. The parameter P$_{o}$ represents the equilibrium spontaneous polarisation. It can be seen from Eqs.(13) to (16), that the dynamic magnetic and electric components are not coupled directly. Hence, the susceptibilities can be written as 

with magnetic components given by 

Here ω 2 afm = ω$_{a}$ ( ω$_{a}$ − 2 ω$_{ex}$ ) represents the antiferromagnet (AFM) resonance frequency. The frequency Ω$_{me}$ is defined as 

<img src='content_image/366764.jpg'>

<img src='content_image/366760.jpg'>

<img src='content_image/366762.jpg'>

<img src='content_image/366761.jpg'>

The frequency Ω$_{o}$ is the frequency shift due to an external magnetic field and is given by 

<img src='content_image/366759.jpg'>

Even though there is no direct coupling between magnetic and electric parts represented by a ME susceptibility, the ME ω$_{me}$ still appears in the magnetic susceptibility, as seen in Eq. (18) to (20). This results from the fact that the canting condition involves the electric polarisation. Finally, the electric susceptibility for χ e xx is 

<img src='content_image/366758.jpg'>

