Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Focused Session: Frontiers in Classical and Quantum Spin Liquids

TT 6.4: Topical Talk

Montag, 14. März 2011, 16:30–17:15, HSZ 03

Fractional spin textures in the frustrated magnet SrCr_9pGa_12−9pO₁₉ — •Kedar Damle¹, Roderich Moessner², and Arnab Sen^1,3 — ¹Tata Institute of Fundamental Research, Mumbai, India — ²Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — ³Boston University, Boston, USA

Quantum mechanics constrains the total electronic spin S of magnetic ions to integer or half-integer values. For an isolated ion with only spin angular momentum and Lande g-factor g_L=2, this results in a magnetic moment of µ=2µ_BS, and a susceptibility (2µ_B)²S(S + 1)/3T, which is approximated by (2µ_B)²S²/3T when spins are treated as classical length-S vectors. Here, we demonstrate that certain vacancy configurations, in a class of corner-sharing networks made up of such spin-S ions coupled antiferromagnetically, give rise to an extended spin texture with classical susceptibility (2µ_B)²(S/2)²/3T.

This corresponds to a fractional moment of µ/2 and represents an instance of fractionalisation yielding a fractional “effective spin” S/2 in a classical setting. This fractional-spin texture leaves an unmistakable imprint on the measured ⁷¹Ga nuclear magnetic resonance lineshapes in the archetypal frustrated magnet SCGO, which we compute using Monte-Carlo simulations and compare with experimental data.