ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Recently, some Al-Mn-Si (Ref. 1) and Al-Mn-Ge (Ref. 2) quasicrystals (with high-Mn and metalloid content) have been reported to show ferromagnetic behavior. The ferromagnetic Al-Mn-Si quasicrystals show low Curie temperature, Tc∼107 K and very weak, strongly field-dependent magnetization (Ms∼0.1 emu/g). The Al-Mn-Ge ferromagnetic quasicrystals are also reported to have low magnetization (∼0.2 emu/g in a field of 20 kOe), fairly high Curie temperature (maximum Tc was quoted for Al52.5Ge22.5Mn25 to be ∼533 K), and also a coercivity in the range of 0.7–1.1 kOe. A crystalline compound close in composition to these quasicrystals, equiatomic AlMnGe,3 is strongly ferromagnetic with a moment at 77 K∼1.7 μB/Mn atom and Tc∼518 K. Many questions are unanswered about these new quasicrystals: Why do they have such low magnetization yet relatively high Tc? Why does Tc increase so strongly when Ge replaces Si? What kind of magnetic order exists in these alloys; is it really ferromagnetic? How many of the transition-metal species are participating in moment formation and what kind of exchange interactions are coupling them? Detailed magnetic measurements on the Al37Mn30Si33 quasicrystals are presented. It has been established that this high-Mn content quasicrystal is not a real ferromagnet and instead shows a concentrated spin-glass behavior with a reentrant ferromagnetism. For the first time a coherent picture of the magnetic phase-diagram of different Mn content Al-Mn-Si, Ge quasicrystals is presented and some of the crucial questions concerning the magnetism in quasicrystal structure have been answered.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.346011
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