Lattice coupled first order magnetoresistance transition in an A-type antiferromagnet: Pr₀.₄₆Sr₀.₅₄MnO₃

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We investigated magnetic, magnetotransport and magnetostriction properties of the A-type antiferromagnet Pr₀.₄₆Sr₀.₅₄MnO₃ which undergoes a first order paramagnetic-antiferromagnetic transition below Tₙ = 210 K while cooling and Tₙ = 215 K while warming. The zero field (μ₀H = 0 T) resistivity shows a sudden jump at Tₙ and a small bump around Tmax = 220 K (> Tₙ). Tₙ shifts down and Tmax shifts up with increasing μ₀H. Magnetoresistance as high as -45-57 % at 7 T is found in the temperature range 180 K-230 K. Isothermal measurements indicate that the field induced antiferromagnetic to ferromagnetic transition below Tₙ is accompanied by a rapid decrease of the resistivity but increase of volume (ΔV/V = +0.25 % at 180 K and 13.7 T). This lattice coupled magnetoresistance transition is suggested due to the field induced structural transition from the low volume orthorhombic to the high volume tetragonal structure.