Why Do Journals Use Inconsistent Magnetic Units?

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Discussion Overview

The discussion revolves around the inconsistencies in magnetic units used in published scientific papers, particularly in the context of magnetization measurements. Participants express concerns about the challenges of comparing results across different studies due to the varied units employed, such as emu, emu/g, and arbitrary units, and the implications for understanding experimental results.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants note that the use of inconsistent magnetic units makes it difficult to compare published results, with only about 1% being comparable.
  • One participant argues that experimentalists should adhere to SI units for clarity, while another mentions that the choice of units is often culture and field-dependent.
  • It is suggested that in some cases, only the relative magnitude of measurements is meaningful, leading to the use of arbitrary units.
  • Another participant points out that the cgs unit for magnetization is emu/cc, which corresponds to 1000 A/m in SI, and emphasizes the importance of specifying sample density when using emu/gm.
  • Concerns are raised about the awkwardness of SI units for describing magnetic phenomena, with some preferring units that are more intuitive for practical measurements.
  • One participant shares their experience with YBCO magnetization data, noting that only a few papers provide sufficient information for quantitative comparisons.
  • Another participant emphasizes that the width of the transition in magnetization data is often more critical than the size of the signal, particularly in assessing sample purity.
  • It is mentioned that susceptibility measurements are frequently reported in arbitrary units, with the focus being on the shape of the curve rather than absolute values.
  • One participant discusses the relevance of measurement methods, indicating that different techniques yield varying insights into material properties, particularly in superconductors.

Areas of Agreement / Disagreement

Participants express a range of views on the appropriateness of different magnetic units, with no consensus on a preferred system. The discussion highlights both the challenges and the contextual nature of unit usage in the field.

Contextual Notes

Participants acknowledge that the choice of units can depend on specific experimental contexts and that some measurements may not provide absolute values that are meaningful for comparison.

nbo10
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What is with magnetic units used in published papers? You can only compare ~1% of the published results. Some of the units I've seen emu, emu/g, Arb, a few don't even give units. How do these papers make it through the review process?
 
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It is surprising and for me annoying,indeed.These experimentalists should be using SI units.Good thing I'm not one of them or one interested in reading their works...

Daniel.
 
nbo10 said:
What is with magnetic units used in published papers? You can only compare ~1% of the published results. Some of the units I've seen emu, emu/g, Arb, a few don't even give units. How do these papers make it through the review process?

The most common units that I have encountered in my line of work is "Gauss". So most of the people in my field publish using those units.

Keep in mind that it is VERY "culture" and field-of-study dependent. In some cases, the relative magnitude is the only thing that is meaningful, so sometime you see in it arbitrary units (arb). Giving exact value may either be not meaningful, or providing something the experiment cannot provide. So you really need to look at this case by case.

It would have helped if you cite specific examples so we have something more definite to go by, rather than just trying to explain this wholesale.

Zz.
 
The cgs unit for magnetization is emu/cc which is 1000 A/m (in SI). If magnetization is specified in either emu/gm (or just emu), there will also be specification (or an implicit assumption of knowledge) of the sample density (or volume).
 
One problem is that SI units are very awkward for describing magnetic phenomena.
They were adopted i a close vote by an international congress, but not by the people who were really caluclating or measuring things. People who do those two things still prefer to use unts more appropriate to the physics.
 
I don't have specific reference handy. I'm going back and looking at magnetization data of YBCO and how the YBCO was processed. Of course you can see the qualitative behavior, ie diamagnetic signal at 90K. But I want to compare the size of the signal for different processing. Only a few of the papers give all the information needed to make a quantitative statements.
 
nbo10 said:
I don't have specific reference handy. I'm going back and looking at magnetization data of YBCO and how the YBCO was processed. Of course you can see the qualitative behavior, ie diamagnetic signal at 90K. But I want to compare the size of the signal for different processing. Only a few of the papers give all the information needed to make a quantitative statements.

OK, so now we're getting to the specifics here.

To be fair, the size of the signal is often irrelevant. Unless you think the response is non-linear (which I don't think it is), the amplitude of the signal is not important. What is definitely important is the width of the transition. This is what characterize the degree of purity of the sample, for example. So in your fabrication process, this is what you want to pay attention to more than anything else, I would think...

I see the same thing when people do NMR measurement. The resonance curve often are simply quoted in terms of arbitrary amplitude, because it is the width of the resonance curve that usually is the important quantity. Only in the case where you have a non-linear response would there be a definite need to know the quantitative value.

Zz.
 
This is also especially true in susceptibility measurements. You will often see [itex]\chi[/itex] plotted (vs. T) in arbitrary units. What's important is whether or not there is weirdness in the curve (a sharply peaked susceptibility, for instance), and where (at what T) it happens.
 
well, the size of the signal can be relevant. The question is what kind of method do you use to measure [tex]\chi[/tex]. The simplest thing is to look for AC magnetization, but this is usually a very crude test and the interesting value here is indeed a transition width. Even if people give you the absolute values, they are usually of little use, because you may get the similar (but broader) curve from a good metal.

However the situation is different if you are looking on SQUID data. Now
that is the more close to the material property. Ideal superconductor should expell all the field, which means that its susceptibility is [tex]\chi=-1/4\pi[/tex] in the CGS units ([tex]B=H+4\pi M[/tex]). You can also see the susceptibility per unit of mass, volume, or amount of the matter (per mole).
In SI the susceptibility of the ideal superconductor will be -1.

So if you are looking on the SQUID from ceramic, you may say how much superconducting material do you have. There are other method which can give you the "real" DC [tex]\chi[/tex]




First you need to figure out what
 

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