Phonon scattering and magnetic manifold switching in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mi>GdSm</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mi>Cr</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>
S. Das, Ravi Kiran Dokala, Bruno Weise, Pankaj Kumar Mishra, Rohit Medwal, Rajdeep Singh Rawat, Subhash Thota
Abstract
We report on the temperature dependence of selective phonon scattering and magnetization switching in $(\mathrm{GdSm})\mathrm{Cr}{\mathrm{O}}_{3}$ perovskites. Thermal evolution of key phonon modes ${A}_{1g}(6/5/3)$ and their anomalous change across the antiferromagnetic (AFM) N\'eel temperature $({T}_{\mathrm{N}}\ensuremath{\sim}202\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ endorses the strong spin-phonon coupling in the investigated system. Such changes have been identified in consonance with the vibrational spectrum of trivalent Gd and Cr along with antistretching/bending of $\mathrm{Gd}/\mathrm{Sm}\text{\ensuremath{-}}{\mathrm{O}}_{12}$ polyhedra and $\mathrm{Cr}{\mathrm{O}}_{6}$ octahedra. Further, we find the emergence of many interesting features, such as thermomagnetic irreversibilities of the magnetization, significant enhancement of the ordering temperatures (up to 202 K), and multiple magnetization switching below ${T}_{\mathrm{N}}$ (9.7--85 K) upon the substitution of Sm at Gd sites. We find the presence of kinetic arrest of magnetic phases $[{\mathrm{\ensuremath{\Gamma}}}_{4}({G}_{x},{A}_{y},{F}_{Z};{F}_{R})$ and ${\mathrm{\ensuremath{\Gamma}}}_{2}$ (${F}_{x}, {C}_{y}, {G}_{z}$; ${F}_{x}^{R}, {C}_{y}^{R}$)] along with the presence of nonequilibrium frozen AFM and ferromagnetic clusters ($<30$ K with 70.7% frozen fraction), indicating the presence of a magnetic glassy state which assists the ${\mathrm{\ensuremath{\Gamma}}}_{4}\text{-to-}{\mathrm{\ensuremath{\Gamma}}}_{2}$ phase transition and supports the phase-coexistence nature of the $(\mathrm{GdSm})\mathrm{Cr}{\mathrm{O}}_{3}$ perovskites. Interestingly, Sm moments order across 6.82 K (${T}_{\mathrm{N}}^{\mathrm{Sm}}$), giving rise to yet another phase transition: ${\mathrm{\ensuremath{\Gamma}}}_{26\phantom{\rule{4pt}{0ex}}}({C}_{x\phantom{\rule{4pt}{0ex}}},{G}_{y\phantom{\rule{4pt}{0ex}}},\phantom{\rule{4pt}{0ex}}{C}_{x\phantom{\rule{4pt}{0ex}}};{C}_{x}^{R},\phantom{\rule{4pt}{0ex}}{A}_{y}^{R},{F}_{z}^{R})/{\mathrm{\ensuremath{\Gamma}}}_{27\phantom{\rule{4pt}{0ex}}}({F}_{x\phantom{\rule{4pt}{0ex}}},{C}_{y\phantom{\rule{4pt}{0ex}}},\phantom{\rule{4pt}{0ex}}{G}_{z\phantom{\rule{4pt}{0ex}}};{F}_{x}^{R},\phantom{\rule{4pt}{0ex}}{C}_{y}^{R},{G}_{z}^{R})$. On the other hand, field-dependent $(100\phantom{\rule{0.16em}{0ex}}\mathrm{Oe}\ensuremath{\le}{H}_{\mathrm{DC}}\ensuremath{\le}600\phantom{\rule{0.16em}{0ex}}\mathrm{Oe})$ bipolar switching of magnetization $(\ensuremath{-}7.8/+2.1/\ensuremath{-}12/+16\phantom{\rule{0.16em}{0ex}}\mathrm{emu}/\mathrm{mol})$ at different temperatures below ${T}_{\mathrm{N}}$ under different measurement protocols makes the investigated system a suitable candidate for the magnetic memories and magnetic switches.