Pressure-Modulated Magnetism and Negative Thermal Expansion in the Ho₂Fe₁₇ Intermetallic Compound

Abstract

Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in Ho 2 Fe 17 on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level (E F ), which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials.

Colossal Zero-Field-Cooled Exchange Bias via Tuning Compensated Ferrimagnetic in Kagome Metals

“…The Fe kagome layer (consisting of the 6g (1/2, 0, 0) and 12k ( x , 2 x , z) sites) and the Ho–Fe layer (consisting of the 4f (1/3, 2/3, z ) and 12j ( x , y , 1/4) sites) are alternatively stacked along the c axis. The Fe kagome layers exhibit strong in-plane ferromagnetic (FM) order, but the Ho/Fe layers are in-plane ferrimagnetic (FiM), resulting in an overall ferrimagnetic state . To obtain the compensated ferrimagnetic state, manganese is an ideal candidate for doping since it can decrease the Fe content and introduce extra antiferromagnetic coupling.…”

Giant Negative Thermal Expansion in Ultralight NaB(CN)4

“…Figure 2b shows the density information for the common NTE materials. The density of magnetic alloy NTE materials ranges from 7 to 13 g/cm 3 , attributed to their dense atomic arrangement and the presence of heavy atoms such as TbCo 2 ‐based, [6c] Er 2 Fe 14 B, [22] Ho 2 Fe 17 [23] . Charge transfer materials (SrCu 3 Fe 4 O 12 , YbInCu 4 ) [11c] and ferroelectric materials (PbTiO 3 ‐based) [24] have similar characteristics to to magnetic alloy materials, resulting in relatively high density.…”

Giant Negative Thermal Expansion in Ultralight NaB(CN)4

“…The density of magnetic alloy NTE materials ranges from 7 to 13 g/cm 3 , attributed to their dense atomic arrangement and the presence of heavy atoms such as TbCo 2 -based, [6c] Er 2 Fe 14 B, [22] Ho 2 Fe 17 . [23] Charge transfer materials (SrCu 3 Fe 4 O 12 , YbInCu 4 ) [11c] and ferroelectric materials (PbTiO 3 -based) [24] have similar characteristics to to magnetic alloy materials, resulting in relatively high density. For most open-framework NTE materials, the density is reduced from ~7 g/cm 3 to ~2 g/cm 3 .…”