Crystal field, Dzyaloshinsky-Moriya interaction, and orbital order inLa0.95Sr0.05MnO

Abstract

We present a comprehensive analysis of Dzyaloshinsky-Moriya interaction and crystal-field parameters using the angular dependence of the paramagnetic resonance shift and linewidth in single crystals of La0.95Sr0.05MnO3 within the orthorhombic Jahn-Teller distorted phase. The DzyaloshinskyMoriya interaction (∼ 1 K) results from the tilting of the MnO6 octahedra against each other. The crystal-field parameters D and E are found to be of comparable magnitude (∼ 1 K) with D ≈ −E. This indicates a strong mixing of the |3z 2 − r 2 and |x 2 − y 2 states for the real orbital configuration.

Orbital order parameter inLa0.95Sr0.05MnO3

“…From these crystallographic g-values, the local g values of Mn 3+ can be calculated as g z =1.977, g y (=g b )=1.986, and g x =1.995, typical for ions with less than half-filled 3d-shell with the longest and shortest Mn-O bond along the local z and x direction, respectively [18]. The main result of this evaluation is the E/D-ratio, which we improved in comparison to our previous estimate [13] by the Q-band experiment. For H ext applied along the b-axis the data are nearly T -independent, whereas they clearly exhibit the CW behavior for the other orientations.…”

“…Only near the minimum below 200 K the absolute values are slightly enhanced at 34 GHz as compared to 9 GHz. Whereas the g-values obtained at X-band frequency bear a rather large uncertainty [11,13], at Q-band frequency the gvalues show a regular T -dependence, approaching a constant high-temperature value and increasing for T → T N . First, we determined the ZFS parameters D and E from the T dependence of H res at Q-band frequency.…”

“…The orbitally ordered O ′ -phase is characterized by an anisotropy of ∆H [11,12], which for polycrystalline samples reduces to a broad maximum in ∆H(T ) [9,10]. Previously, the angular dependencies of ∆H and the resonance field H res had been analyzed for 200 K and 300 K in high-temperature approximation, allowing to estimate the Dzyaloshinsky-Moriya (DM) interaction and the strength of the zero-field splitting (ZFS) parameters [13]. At X-Band frequencies (9 GHz) ∆H was of the same order of magnitude as H res and due to the overlap with the resonance at −H res and their mutual coupling via the nondiagonal elements of the dynamic susceptibility [14] the values for H res contained a rather large uncertainty.…”

“…First, we determined the ZFS parameters D and E from the T dependence of H res at Q-band frequency. Using the general formula for the resonance shift due to crystal field (CF) effects [13,16] and accounting only for the rotation (angle γ) of the MnO 6 octahedra in the ac plane (axis notation like in Ref. 17), we obtained the following expressions for the effective g-values for H ext applied…”

“…First, we determined the ZFS parameters D and E from the T dependence of H res at Q-band frequency. Using the general formula for the resonance shift due to crystal field (CF) effects [13,16] along one of the crystallographic axes…”