Abstract
The origin of magnetism in metals has been traditionally discussed in two diametrically opposite limits: itinerant and local moments. Surprisingly, there are very few known examples of materials that are close to the itinerant limit, and their properties are not universally understood. In the case of the two such examples discovered several decades ago, the itinerant ferromagnets ZrZn2 and Sc3In, the understanding of their magnetic ground states draws on the existence of 3d electrons subject to strong spin fluctuations. Similarly, in Cr, an elemental itinerant antiferromagnet with a spin density wave ground state, its 3d electron character has been deemed crucial to it being magnetic. Here, we report evidence for an itinerant antiferromagnetic metal with no magnetic constituents: TiAu. Antiferromagnetic order occurs below a Néel temperature of 36 K, about an order of magnitude smaller than in Cr, rendering the spin fluctuations in TiAu more important at low temperatures. This itinerant antiferromagnet challenges the currently limited understanding of weak itinerant antiferromagnetism, while providing insights into the effects of spin fluctuations in itinerant–electron systems.
Highlights
The origin of magnetism in metals has been traditionally discussed in two diametrically opposite limits: itinerant and local moments
The value of the temperature-independent Pauli susceptibility, calculated from taehg.mere.eums. amgwonelelÀtlic1.wUditehpnosnitthywe aorefmxpisnteagrtiemasbeonwvt0aeEl th0o.e2neNÂe1eM0l 0Àt/eH3meEp.me0r..ua3t.uÂmreo1,0l ÀtÀh1e3, inverse susceptibility H/(M–M0) is linear in temperature up to 800 K. Such linear T dependence of H/M has been long considered the hallmark of local moment magnetism, until it was observed in the weak itinerant ferromagnets (IFMs) without local moments, ZrZn2 and Sc3In
TiAu is an itinerant antiferromagnet (IAFM), and no existing theory accounts for an IAFM ground state if neither Ti nor Au have conventional local moments
Summary
The origin of magnetism in metals has been traditionally discussed in two diametrically opposite limits: itinerant and local moments. In the case of the two such examples discovered several decades ago, the itinerant ferromagnets ZrZn2 and Sc3In, the understanding of their magnetic ground states draws on the existence of 3d electrons subject to strong spin fluctuations. We report evidence for an itinerant antiferromagnetic metal with no magnetic constituents: TiAu. Antiferromagnetic order occurs below a Neel temperature of 36 K, about an order of magnitude smaller than in Cr, rendering the spin fluctuations in TiAu more important at low temperatures. The local and itinerant moment are extreme limits of magnetic behaviour, with poorly understood physics associated with in-between scenarios. The long-range order is confirmed by neutron diffraction data, while muon spin relaxation (mSR) experiments indicate static order Together these measurements point to small moment ordering in the whole sample volume. In addition to the experimental evidence for the itinerant moment antiferromagnetic order in TiAu, density functional theory (DFT) calculations confirm the spin density wave (SDW) small moment ordering
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