Static and dynamic magnetization control of extrinsic multiferroics by the converse magneto-photostrictive effect

In this work, photostrictive manipulations of static and dynamic magnetic properties are demonstrated in an extrinsic multiferroic composite. The photostriction is achieved with visible light in the blue region of the spectrum. The composites consist of 5 nm or 10 nm magnetostrictive Fe$_{81}$Ga$_{19}$ thin films coupled to a piezoelectric (011)-Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$-Pb(Zr,Ti)O$_3$ substrate. Angular dependent magnetization reversals properties are largely enhanced or reduced under a converse magneto-photostrictive effect (CMPE). The CMPE strength is analysed with a novel coefficient named the converse magneto-photostrictive coupling coefficient. This coefficient is proposed as a general approach to analyse and to compare different extrinsic multiferroics under the converse magneto-photostrictive effect. Its thickness dependence reveals that the CMPE strength decreases with an increase of the Fe$_{81}$Ga$_{19}$ thickness. Experimental evidence for a control of dynamic magnetic properties under CMPE is then revealed by ferromagnetic resonance measurements. Resonant fields are shifted under CMPE, whereas their linewidths remain constant. Furthermore, resonant field shifts can be either positive or negative depending on the in-plane angle. The largest shift under CMPE of +5.7 % is obtained for the 5 nm sample. Our study shows that the CMPE provides an efficient approach for a control of not only the static but also the dynamic magnetic properties in extrinsic multiferroics.