Eyup Duman

Publications (25) View all

• Article: Antiferromagnetic-ferromagnetic crossover in La_ {0.5} Pr_ {0.5} Mn_ {2} Si_ {2} and its consequences on magnetoelastic and magnetocaloric properties

  B. Emre, S. Aksoy, O. Posth, M. Acet, E. Duman, J. Lindner, Y. Elerman
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  ABSTRACT: La0.5Pr0.5Mn2Si2 exhibits an antiferromagnetic-ferromagnetic transition caused by the crossover of the critical distance between Mn atoms on changing temperature. Applying a magnetic field in the antiferromagnetic state can cause a field-induced transformation to the ferromagnetic state at a critical field, which increases with decreasing temperature. We study here with magnetization and strain measurements the magnetic-field-induced strain associated with the field-induced transformation and magnetocaloric effects close to the transition temperature. We also examine the temperature dependence of the critical field and find from magnetization and ferromagnetic resonance measurements that short-range ferromagnetic correlation among the rare earth and Mn-sublattices occur at low temperatures. At low temperatures, this causes a decrease in the critical field for the crossover from antiferromagnetic to ferromagnetic coupling with decreasing temperature.
  Phys. Rev. B. 10/2008; 78(14).
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  Available from: Eyup Duman

  Article: Magnetic instabilities in Fe3C cementite particles observed with Fe K-edge x-ray circular dichroism under pressure.

  E Duman, M Acet, E F Wassermann, J P Itié, F Baudelet, O Mathon, S Pascarelli
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  ABSTRACT: The ferromagnetic interstitial iron compound Fe(3)C (cementite) is expected to have Invar properties, whereby a high-moment to low-moment transition should occur when the atomic volume is reduced below a critical value. We, therefore, examine the pressure dependence of the Fe K-edge x-ray magnetic circular dichroism in Fe(3)C at ambient temperature and pressures up to 20 GPa. We find clear evidence for a high-moment to low-moment transition around 10 GPa.
  Physical Review Letters 03/2005; 94(7):075502. · 7.37 Impact Factor
• Article: Large spontaneous magnetostrictive softening below the Curie temperature of Fe3C Invar particles

  E. Duman, M. Acet, T. Hulser, E. F. Wassermann, B. Rellinghaus, J. P. Itie, P. Munsch
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  ABSTRACT: Fe ₃ C incorporates only Fe as a metallic element and is an Invar material with valence electron concentration 8.67. We have studied the equation of state up to 20 GPa of Fe ₃ C particles (d∼40 nm ) below and above the Curie temperature (room temperature and 550 K , respectively) to search for a softening associated with a magnetovolume instabilities characteristic of Invar-type material. The isothermal bulk modulus of Fe ₃ C particles at room temperature was found to be about 13% smaller than that of the value at 550 K . This difference is comparable with the relative difference in the bulk modulus of Fe ₆₅ Ni ₃₅ Invar in a similar temperature range around the Curie temperature.
  Journal of Applied Physics 12/2004; · 2.17 Impact Factor
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  Article: Magnetovolume instabilities in the pressure dependence of the K-edge circular dichroism of Fe3C Invar particles

  E. Duman, M. Acet, E.F. Wassermann, J. P. Itie, F Baudelet, O Mathon, S Pascarelli
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  ABSTRACT: The p-electrons of carbon in the interstitial compound Fe3C hybridize with the Fe d-band and enhance the valence electron concentration of Fe from 8 to 8.67. At this concentration, substitutional 3d transition metals and alloys exhibit strong moment-volume coupling phenomena and associated magnetovolume instabilities, otherwise known as the Invar effect. For this reason, Fe3C is also expected to incorporate a strong magnetovolume instability, and therefore, we examine the pressure dependence of the of the K edge x-ray magnetic circular dichroism in Fe3C at ambient temperature and pressures up to 20 GPa. We and clear evidence for a high-moment to low-moment transition at about 10 GPa.
  11/2004;
• Article: Criticality in Cu-Al-Mn hysteresis loops

  J. Marcos, E. Vives, Ll. Ma�osa, A. Planes, E. Duman, M. Acet
  Journal of Magnetism and Magnetic Materials. 05/2004; 272-276:E515--E516.